Steven
Thank you for your reply.
Following the advice received, I made a gallery with various patterns and tested it.

In conclusion, I changed the type of transition from Slide to Fade and got a normal display.

Changing other parameters did not solve the problem in particular. For example Transition Time or Caption Position.

If you create it with Transition Type set to Fade and browse the image with the arrow keys on the keyboard in MacOS Safari, file name mismatch will occur for a moment.
However, when the Transition Type is Fade, the portion of the file name which was displayed out of the way has been refreshed and switched to the display of the correct file name.

The operation of saying "This file is refreshed and displayed correctly" did not occur when Transition Type was Slide. It only happened at the time of Fade in Mac OS Safari.

I hope this information is useful information for developers.

Also, the address of the server used when capturing the video is as follows.

https://sarw.mixh.jp/imageFileNameMatchTest/

In the meantime, we will create a gallery with Fade for Transition Type.

Thanks for the advice.

I forgot to write down the environment.

Juicebox pro v 1.5.1
It is a gallery created using Lightroom Plugin.

The latest version of MacOS HighSierra

However, the problem that this filename does not match occurred from the time of using Juicebox v1.4.