A bug was reported where user profile settings do not reflect group membership after bulk inviting users to a group. kmvoges shared an error message and log details, and sam requested that it be added to the fix list. techAPJ initially could not reproduce the issue, but later kmvoges provided repro steps and screenshots using a CSV invite method. The issue was further clarified by sam, who mentioned that no error message is displayed when trying to add a user who already exists in the group. The bug was eventually fixed by techAPJ via a GitHub pull request and commit.
So seemingly users are being added to the group, they also have access, only the profile settings do not correctly reflect the fact that they have been succesfully added to the group.
I just tested this on my dev env and I am unable to repro this.
I invited a user via bulk invite feature and specified group beta to be added by default. When the user redeemed that invite, I can see that he has been added to beta group.