"Videos" are not shown in the media library?

I did a screen recording with the chrome extension.

Now I want to insert it into an interactive supademo. I can not add this screen recording in any way. It is now shown in the “media library” and the download of the screen recording gets stuck at 26% every time.

The chrome extension finds both my webcams and I can select between them. The “record screen”-feature from the supademo webpage finds both but no matter which one I click it only chooses the Logitech one. Bug? It worked fine yesterday to select any of the two cameras.