Interactive videos not working on android mobile inside course presentation.

I'm not sure if this fits best in the bugs or the content creation forum, but I'll put it here since it's a problem i hope can be fixed.

I'm trying to make minimal pair excercises for distinguishing between vowels in the Swedish language. I want the student to hear a word, choose which one it is, and after the answer i want a video to be played where the two vowels are compared. Finally (after 20-30 minimal pairs) the excercise should end with a total score. I found a way to do it using a Course presentation with embedded Interactive videos. You can try it here:

svenskamedflyt.com/test-h5p

It works fine on my windows computer, however when i try on my android phone only the first videos work. When I reach slide 9 and 10, there is an error message: "Unable to decode media". However if i go straight to slide 9 and 10 they will work, but videos in some other slides will get the error message instead. It's always two videos that don't work. (update: since i added poster images to the videos the error message doesn't appear right away, but if you start all the videos it appears in the ninth and tenth video that you try to start.)

This problem happens every time i try the excercise on my mobile, but never on my computer. My students will use it mostly on their mobiles, so it has to work there. Any ideas? I tried with youtube videos but got other problems with that, so that's not an option. I hope this can be fixed, or I'll have to find another way to make the excercise. Any suggestions for other ways to make the same kind of excercise would be very welcome too!

Details:

Platform and version number. E.g. Drupal, Wordpress, Moodle: Wordpress 5.0.3
Mobile or Desktop: The problem only appears on mobiles
Browser: Chrome, Firefox, Safari etc: Chrome
H5P plugin version: H5P Version 1.11.3
H5P content type and version (if a content type was used), and a sample URL or attached H5P: Course presentation, svenskamedflyt.com/test-h5p

I tried these things myself with no success:

• I changed the quality of the videos to make them less heavy.
• I cleared cache and cookies in the chrome browser on my mobile.
• I added "poster images" to the videos (thinking it might somehow prevent them from loading directly when to page is opened). After this, the first question appears in all the videos, but two of the videos still do not play (same error message as before).