I have developed a web application (wordpress) that shows a number of thumbnail images, each connected to an mp4 video. There is custom javascript such that if a user selects a number of thumbnail images, creating a playlist, all of the associated videos will play back in the order selected. This works perfectly in the Chrome, Edge, Safari, and Opera browsers. However, in Firefox, rather than playing back the videos in sequence, after each video, a gray screen appears in the video player (JWPlayer) that says the file is corrupted. The mp4 files are not corrupt since they work well in the other browsers. Also, once that gray box appears, by clicking the "Play Video"button the next video in the sequence will play but this must be repeated after each video in the playlist. Is there a setting that can be adjusted so that sequence will play in FIrefox? Is there a default setting that prevents the sequential playback?

Any help would be appreciated