Clicking the Info Button toggles all content on the overlay (except for the Button Bar itself) including the Back Button if backButtonPosition="OVERLAY".
If you do not want the Back Button to be toggled on and off when the Info Button is clicked, then try setting backButtonPosition="TOP" instead. You could also set buttonBarPosition="TOP" to keep the Back Button and Button Bar on the same level.

Reference links:
Button Bar: https://www.juicebox.net/support/config … ar-options
Back Button: https://www.juicebox.net/support/config … on-options

It sounds like the problem might be due to images being scaled to different degrees in different browser viewport sizes and aspect ratios.

If you currently use imageScaleMode="SCALE", which scales down large images if necessary and also scales up small images (which can reduce their visual quality), then I would recommend that you use larger source images in your gallery so that images do not need to be scaled up. In addition to this, you could set imageScaleMode="SCALE_DOWN" (the default value) which would ensure that small images are never scaled up.
I hope this helps.

If you'd like me to take a look to see if I can help further, then please post the URL to your gallery's web page.
If you are not currently using a gallery layout which exhibits the problem, then perhaps you could upload a couple of screenshots somewhere so that I can at least see what you are seeing.
Of course, if you are happy with the current situation, that's absolutely fine.

Many thanks for providing the links to your test galleries.

Using slightly larger images in your gallery might help.
I notice that your current images are 900px x 600px and, when using imageScaleMode="SCALE_DOWN", they will not be scaled up to fill the gallery's image area in a large viewport.
Using larger images should help to ensure that the images are displayed as large as possible within the gallery's image area.
Give it a try in another test gallery (perhaps using image dimensions of 1152px x 768px) and see how you get on viewing it on your iPad Air.

As long as the images are larger than the gallery's image area (which, in a responsive gallery, will depend on the size of the user's browser window), Juicebox will dynamically scale them down slightly to fit within the available space (and they will be displayed as large as they can be within the given area).

If you still see some degradation of image quality (even using larger images in your gallery), they try viewing the gallery in a different browser (Mobile Chrome, Mobile Firefox, Mobile Safari) to see if this makes a difference. Different browsers will likely have different resizing algorithms and you might find that certain browsers give more visually pleasing results than others when images are not displayed at their actual size. (Unfortunately, there is nothing that Juicebox can do to change the way that a browser displays an image at a specific size but it might be worth trying to at least eliminate browser differences as a possible cause.)

Hopefully this will help.