I have found the issue.
Previously settings have been used for extra block creation, now it's customSettings
Changing everything accordingly fixes issue.
You can add the same user into one group multiple times via the admin panel
This post is deleted!
Does it annually do anything? Does the user show up multiple times in the group list or anything?
It doesn't get saved which is good. So only the admin panel has this "bug", where you can add the same user multiple times, but it gets removed once you save the group and reload your tab. So nothing critical.