The main problem is that smb/cifs share in fstab aren’t working anymore.
Research and testing with new datasets, shares, users and groups shows that resetting the password could be a solution.
But you get an error, if the user is a member of a builtin group.
Validation Error
[EINVAL] user_update.groups.6: www-data: membership of this builtin group may not be altered. [EINVAL] user_update.groups.8: docker: membership of this builtin group may not be altered.
More info…
When I remove the user of all the group(s) changing the password will work.
But then you get another problem. You cannot add the user to the builtin group again, of which before he was a member.