Some days ago I upgraded a restored Moodle 3.4 to 3.5, and found that some videos could not be played if they had spaces in the filename. Then I successfully restored and upgraded Moodle once more. Now after having upgraded the production site the problem is back though in a slightly different way. Now it is not the spaces in the file names that causes the trouble, now I can not fix it.
Initially the video is just black with a white error message, in English something like "Video playback was interrupted due to broken data or because the video used facilities that your browser does not support." After removing spaces in the filename the video is just shown with a wheel running as if it never gets loaded. Trying to link directly to the video URL in the browser gives an error message like "The video can not be played because the file is corrupt." If I download the file I can play it just fine locally.
Strange is it that most of our mp4 files can be played in Moodle just perfect.