Hi Anselm,
Sorry you are experiencing these issues.
Thank you for the video you shared showing the steps to reproduce this. It is helping troubleshoot this.
I noticed in the video you shared that the Screencast you were trying to manage access is the Screencast 7F37E06E-81A6-40CA-AC34-038047761324
The Screencast Author is the one with the account login credential starting with … “Lehrbeauf…”. So I am assuming you were signed as this user when you recorded the video you shared.
The groups listed for this Screencast in the Manage Access page should have been the…
“Gruppe BIWB” - 2AFADC60-D72B-4620-84F5-DCEBE73D287D
“Gruppe UIWB” - 6C7A38EE-038C-452D-A8DE-84C45E314FB1
…I am not sure yet why the Group “Gruppe BMB” - 9B0E1716-6948-411A-B642-E7C1D76BE333 was listed for this Screencast since our records indicate that the user “Lehrbeauf…” is not a member of this group, and the Screencast has not currently been granted access to this Group …

… I did a test on my end and this group is not retrieved for this Screencast/User. It is quite possible what I am seeing on my records does not reflect what we had when you recorded the video you shared.
Note that in the video you sent you tried to edit the Group “Gruppe BMB” - 9B0E1716-6948-411A-B642-E7C1D76BE333
I wonder if you were removed from this Group and there was a race issue, or there is a cache issue.
A Problem I see with Group “Gruppe BMB” - 9B0E1716-6948-411A-B642-E7C1D76BE333 is that no one seems to be the owner right now. Not sure how it got to this orphan ownership state but this could be causing issues.
It is hard to troubleshoot this since we don’t have all the records of events that happened with all the groups associated with your two users, and its membership.
I am engaging the QA team to look at this and try to reproduce this issue. It is quite possible that there is a bug there. We haven’t seen anyone report this though.
For now, I suggest us to straight out the ownership of the Groups for your two users. Please let me know which Groups should your two users own…
This is what I see today…
User Login “Lehrbeauf..”
Own these two Groups….
“Gruppe UIWB” - 6C7A38EE-038C-452D-A8DE-84C45E314FB1 - This group is setup to allow only owners to grant Screencast access
“Gruppe BIWB” - 2AFADC60-D72B-4620-84F5-DCEBE73D287D - This group is setup to allow only owners to grant Screencast access
User Login “anselm.kunz@...”
Is member of Group…
“Gruppe BIWB” - 21A2E8B6-9866-4823-AFC0-DC035E4AFF14 where he is not the owner. This group is setup to allow only owners to grant Screencast access.
Has been invited, and not accepted yet, invitations for these groups…
“Test Gruppe” 654A89E8-876D-444A-A777-2DEA445A3314
“Gruppe UIWB” - AD29C9FF-DAB6-4C28-BEE8-53BB6B137295
“Gruppe UIWB” - 6C7A38EE-038C-452D-A8DE-84C45E314FB1
“Gruppe BMB” - 9B0E1716-6948-411A-B642-E7C1D76BE333
… Please let me know if the ownership above is correct and/or if you need to have the unaccepted Group invitations set to accepted.
One thing I would also suggest for now is to make sure you sign-out and close your browser before signing in as a different user. I wonder if there is a cache issue somewhere.
We will try to reproduce these issues on our end and let you know what we found out.
Regards,
Eduardo