I'm glad to hear that you've got it working!
Thank you for posting back to let me know.

The problem is almost certainly a z-index issue.
Juicebox uses z-index values to ensure that certain elements (such as captions and navigation hit areas) are stacked on top of other elements (such as the main images) within the gallery.

To resolve your problem, assign a z-index value of 9999 to your menu system via CSS to ensure that your menu is stacked on top of all gallery elements.

If you have any trouble doing this, then please post a link to your gallery's web page so that I can see the problem for myself (live in your web page rather than just a screenshot) and, with the help of a browser's developer tools, determine which CSS class or id the z-index value should be assigned to.
Thank you.

Just to let you know, you can have multiple lines in image titles and captions by using HTML line breaks (<br>) within them.
For example:

<caption><![CDATA[Line #1<br>Line 2]]></caption>

If entering such a caption within JuiceboxBuilder-Pro, you just need to enter:

Line #1<br>Line 2

JuiceboxBuilder-Pro will automatically add the <caption> and CDATA tags when the caption is written to the gallery's 'config.xml' file.

All image titles and caption will use the styling from the configuration options such as textColor ('Customize -> Lite' section) and galleryFontFace ('Customize -> General' section).
For reference, a list of all configuration options can be found here.

Please post a link to your gallery so that I can see the problem for myself and hopefully help further.
Thank you.

Thank you for the update.
I'm glad you've found the cause of your problem and have managed to get JuiceboxBuilder-Pro up and running again (although it's certainly strange that Avast did not give you the opportunity to make an exception for JuiceboxBuilder-Pro the first time it encountered it).

I would be very grateful if you could provide me with the following information so that I can log a false positive report with the Avast team.

(1) The version of JuiceboxBuilder-Pro that you are using ('Help -> About JuiceboxBuilder-Pro...').

(2) The versions of Avast that you are using (both the program version and the database version).

(3) The element of Avast which triggers the warning (Ransomware Shield or something else).

Thank you.

I notice that you are currently using Juicebox v1.5.0.
I would recommend upgrading to the latest version (v1.5.1) as many bugs were fixed in v1.5.1. (There are 40 documented bugfixes in the Version History.)

Having said that, I think your problem may simply be due to aspect ratio differences between your images and mobile viewing devices.

When I view your gallery on my iPod Touch, the gallery's Splash Page appears in the embedding page with very little space surrounding it (the Splash Page takes on the gallery dimensions set in the embedding code) and, when the Splash Page is tapped, the gallery expands to fill the viewport (regardless of the gallery dimensions set in the embedding code).
In the expanded gallery, your landscape-style images are displayed as large as possible (without cropping) in a portrait-style viewport but with white areas above and below the images.
If the images were displayed any larger, then cropping would occur and the left and right sides of the images would be missing.
When I rotate my iPod Touch, the images are displayed much larger (as the landscape orientation closely matches the aspect ration of your images) with only a little white space to the left and right of the images.

There's probably little you can do to reduce whitespace in your expanded gallery but Juicebox will always display the images as large as possible within the gallery's image area (no matter what size and shape the gallery is) unless imageScaleMode is changed from its default value of SCALE_DOWN.

I hope this helps to clarify things somewhat.

Please also see this FAQ:
My Juicebox gallery shows too much space above or below the main image, how do I fix this?

Here are some tips which may help:

(1) First of all, if you have any security software installed (e.g. Avast, AVG, etc.), please make sure that the program itself and its database are both up to date.
If this does not help, then try completely disabling your security software (at your own risk) or make an exception for the JuiceboxBuilder executable file to see if this makes a difference.
(Older versions of Avast's Ransomware Shield have been known to interfere with the functionality of JuiceboxBuilder but this should not be a problem with up-to-date versions.)

(2) With JuiceboxBuilder-Pro closed, delete the following folder manually and then try running JuiceboxBuilder-Pro again:
Mac: /Users/Username/Library/Application Support/Adobe/AIR/ELS/JuiceboxBuilder-Pro
Windows: C:\Users\Username\AppData\Roaming\Adobe\AIR\ELS\JuiceboxBuilder-Pro

(3) With JuiceboxBuilder-Pro closed, please check to see if the following folder exists on your system:

C:\Users\Username\Documents\JuiceboxBuilder-Pro\.tempGallery

(I'm not sure what the equivalent location would be for a Mac but if you search for ".tempGallery" you should hopefully find it.)
If there is a .tempGallery folder in this location, please delete it manually.
The .tempGallery folder is created automatically by JuiceboxBuilder for internal use only (for the live preview window and as a temporary gallery folder until the gallery is saved on the 'Publish' tab).
It should automatically be deleted by JuiceboxBuilder-Pro on closing the application but, if this fails, it has been known to render the 'New Gallery...' and 'Open Gallery...' buttons inactive.

The only way that I've been able to replicate the symptoms that you describe myself is to save a gallery to a Google Drive folder (so I'd recommend not saving a gallery to a location which is being synced to an online file sharing service) and the problem seems to be due to a persistent .tempGallery folder (which has not been removed as expected).
You may not be using a Google Drive folder but a persistent .tempGallery folder might still be causing a similar problem.

If all else fails, try completely uninstalling both JuiceboxBuilder-Pro and Adobe AIR following the procedure below.

(1) Uninstall JuiceboxBuilder-Pro.
Mac: Delete the 'JuiceboxBuilder-Pro' file from the Applications folder and empty your Trash.
Windows: Use the uninstaller in the 'Control Panel -> Programs -> Uninstall a program...' list.

(2) After uninstalling JuiceboxBuilder-Pro, please check that there are no files are left behind (even from a failed installation) by manually deleting the following folders (if they exist) from your hard drive:
Mac:
/Applications/JuiceboxBuilder-Pro.app/
/Users/Username/Library/Application Support/Adobe/AIR/ELS/JuiceboxBuilder-Pro
/Users/Username/Library/Preferences/JuiceboxBuilder-Pro
Windows:
C:\Program Files (x86)\JuiceboxBuilder-Pro
C:\Users\Username\AppData\Roaming\Adobe\AIR\ELS\JuiceboxBuilder-Pro
C:\Users\Username\AppData\Roaming\JuiceboxBuilder-Pro
C:\Users\Username\Documents\JuiceboxBuilder-Pro
You may need to show hidden files to find some of the above locations in Windows File Explorer.

(3) Also, please follow the procedure above (Steps #1 - #2) for JuiceboxBuilder-Lite, too (if you have it installed).
JuiceboxBuilder-Lite and JuiceboxBuilder-Pro can both be installed and run side by side on the same computer but, being that you are experiencing problems, it might be wise to completely clear your system of all JuiceboxBuilder files before trying to reinstall JuiceboxBuilder-Pro.

(4) Uninstall Adobe AIR.

(5) Reinstall Adobe AIR.
You can download the latest version of Adobe AIR from here.

(6) Reinstall JuiceboxBuilder-Pro (and make sure that it is the latest version, v1.5.1) following the instructions here.

Hopefully this will help.
Please let me know how you get on.

Thanks!

If you find that many small thumbnails are displayed, then try scaling the content of your web page for mobile devices by adding the following <meta> tag to the <head> section of your web page:

<meta name="viewport" id="jb-viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1, maximum-scale=1, user-scalable=0" />

The thumbnails look larger after clicking the Splash Page because, when the Splash Page is clicked, the gallery is expanded on a web page of its own (the 'full.html' web page from within the gallery's 'jbcore' folder) and this web page already has the <meta> tag from above in place.

When a Juicebox gallery is displayed on a touch-enabled mobile device, Juicebox uses Touch Input Mode (rather than Mouse Input Mode). Please see the Input Mode support section for more information.

In Touch Input Mode, the imageTransitionType is always set to SLIDE (which is the transition which best fits with the swipe gesture for navigating between images).
The imageTransitionType can be set only for Large Screen Mode and Mouse Input Mode. This is noted in the short description for imageTransitionType in the Main Image section of the Config Options Page:

Unfortunately, there is no way to change the imageTransitionType on a touch-enabled mobile device. It will always be set to SLIDE.

Please feel free to post suggestions for future versions in the Feature Requests forum thread.
This keeps all the ideas together and ensures that they are not overlooked by the developers.
I do not know the likelihood of any suggestions being implemented but this is certainly the best place for all ideas.
Thank you.

Unfortunately, as you have discovered, the current version of WP-Juicebox (v1.5.1) is not compatible with the new Gutenberg editor within WordPress 5.0 (and later).

We hope to release a version of WP-Juicebox which is compatible with WordPress 5.0 very soon.
In the meantime, there are two things that you can do.

(1) Install and use the Classic Editor plugin (written and maintained by the WordPress team) from here.
This replaces the Gutenberg editor in WordPress 5.0 with the familiar TinyMCE editor and, in doing so, restores WP-Juicebox functionality.

... or:

(2) Try the new version of WP-Juicebox which you can download from here.
It has not yet been released but it has been designed to work with the Gutenberg editor in WordPress 5.0.
The new plugin adds an 'Add Juicebox Gallery' button to the Gutenberg toolbar which, when clicked, displays the regular WP-Juicebox gallery settings window.
After clicking the 'Add Gallery' button, the WP-Juicebox gallery shortcode is entered into the page or post as a Gutenberg 'Shortcode' block.
Here's how to then add images to your WP-Juicebox gallery (essentially attaching images to the page or post) from within Gutenberg:

• Add a Gutenberg 'Gallery' block to the page or post containing the WP-Juicebox gallery shortcode.

• Upload images from your local machine by clicking the 'Media Library' button (in the 'Gallery' block) and dragging and dropping the images into the media window.

• Wait until the images have finished uploading.

• Reorder the images (if necessary) by going to the 'Create Gallery -> Media Library' section, selecting 'Uploaded to this post' and then dragging and dropping the images into the order you require.

• Close the media window using the cross at the top right (do not click 'Create a new gallery').

The new version of the plugin also adds the ability to create a new gallery on the 'WP-Juicebox -> Manage Galleries' page.
This is simply an alternative way to create a new gallery when using an editor which does not support the 'Add Juicebox Gallery' button (such as CodeMirror).
After creating a gallery via this method, you would need to copy and paste the shortcode into the page or post (and then attach images to the page or post as usual).

If you are a Juicebox-Pro user, please remember to upgrade the plugin to Juicebox-Pro (as it comes bundled with Juicebox-Lite) by following the instructions here.

Please remember that the plugin has not yet been released and is still officially in an experimental state (although I have tested it myself and it should work fine).
If you choose to try the new plugin, please let me know how you get on and if I can be of any further assistance.

What you are describing is the Splash Page.

On mobile (small screen) devices, if the gallery is embedded in a web page alongside other content, then Juicebox displays the Splash Page (an image placeholder for the gallery) which, when tapped, expands the gallery to fill the browser viewport (to give the main images as much room to be displayed as possible).
In Small Screen Mode, after tapping the Splash Page (or if the gallery is presented on a web page of its own and the Splash Page is not used), the user will be presented with a grid of thumbnails from which a main image can be selected.
When a thumbnail is tapped, the thumbnail page is replaced with the chosen image. (In Small Screen Mode, the thumbnails and main images are displayed on different pages to maximize the area available for the images on small screen devices.)
The user can return to the thumbnail page by tapping the 'Thumbnail' button on the gallery's Button Bar (and can return to the original embedding page by tapping the 'Close Gallery' button).
Please see the Screen Modes support section in the Gallery Tour for more information.

Yes, it is not a matter of changing the gallery's size but rather setting specific configuration options.

You can choose to not use the Splash Page by setting showSplashPage="NEVER" (in  JuiceboxBuilder-Pro's 'Customize -> Splash Page' section). Using this setting, the thumbnail page would initially be displayed instead of the Splash Page on small screen devices. If you want to skip the thumbnail page and go straight to the first main image in the gallery, then set showSmallThumbsOnLoad="FALSE" ('Customize -> Thumbnails').

Alternatively, you could force the gallery to be displayed in Large Screen Mode (which, by default, does not use the Splash Page and displays the thumbnails and main images together, like in desktop browsers) on all devices and in all browsers by setting screenMode="LARGE" ('Customize -> General').

If you choose to continue to use the Splash Page, then you can configure it (for example to change the image displayed) using the Splash Page configuration options listed here.

I hope this helps to clarify things and gives you a few options to try.

It looks like all your images (both landscape and portrait) are justified left due to setting imageHAlign="LEFT" in your gallery's 'config.xml' file.
Setting imageHAlign="LEFT" will ensure that the left-hand edge of each image is flush against the left-hand edge of the image area within the gallery.
Set imageHAlign="CENTER" instead (the default value) and your images will all be horizontally centered within the gallery's image area.
For reference, imageHAlign can be found in JuiceboxBuilder-Pro's 'Customize -> Main Image' section.

If you save each gallery to its own unique folder and re-save a specific gallery to its own specific folder, then no other gallery folders should be touched when re-saving the gallery.
I cannot replicate the problem you describe but it you can provide a certain folder structure and set of instructions which will allow me to reproduce the problem, I'll certainly be happy to investigate further.
Thank you.