I've created a Personal Teams App with Teams App Studio. Simple SharePoint communication site with some Stream Videos included. For most of the people the app is working completely fine. But for some users (5%) the Stream videos cannot load and they get this error screen. If they click sign-in they are redirected to an error page.
As soon as the users are testing the "Public Preview" Teams version, the app is working perfectly fine and all videos are loading.
It looks like it's a problem with an "older" Teams app version. The other thing that I have in mind, that the user have to renew their authentication as soon as they login with the "Public Preview" version (including MFA).