Playing embedded videos after May update

Hi everybody,

I have a problem with the playback of mp4-videos embedded in pdfs. Before the May update, videos were played by a co-embedded flash video player in the pdf. As you know flash support is going to fade out in December, so Adobe had to change their embedding magic...

The setup is as follows:

I want to use videos in a pdf for a publication. On my Mac I used Acrobat DC pro to embed a video in the pdf and it worked nicely (in Acrobat pro and the free Reader).

Now I move the pdf to my Windows 10 machine (Acrobat Reader, 2020.009.20067), to see if it still works. When I click the play button on the video I get the following error message:

"Acrobat encountered an error while playing this media clip:" (Thats all.)

Opening the file from the explorer works perfectly: you click it, the Windows Media Player pops up, it plays.

I send out the pdf to my coauthors. For some of them it worked (also with the free reader, on Win10 and MacOS). For some of them it did not work with the free reader and one person also reported that the playback crashed his Acrobat DC pro.

I attached a minimal non-working example for you. I created an empty page in Illustrator and then placed a small video with Acrobat DC pro.

Any suggestions to track that problem down are very welcome.

Thanks in advance

-johannes