Video format not supported in some content types
I'm not sure if this is the proper forum for that, but I've encountered a problem using external mp4 video in some content types:
I'm trying to use an externally hosted .mp4 video in branching scenario, course presentation or interactive video. However, I always encounter the error message "video format not supported". The video does work, however, when I add a "video" in the column content type. The video also works just fine when I embed it in normal html5 web pages...
I'm not sure where the root of the problem is: Does H5P require some special codec inside the mp4 container to work reliably or is there some other kind of problem or bug even?
Here is a video where the problem occurs: https://moodle-files.alp.dillingen.de/LFO_MEBIS/video/mebis/mebis_klasse...
I've tested in Chrome and Firefox, running WP 5.1 and the latest H5P update.
What can I do?