We have some crazy stuff going on. We can add members to Domain Admins and they stay some time, but after a while they are removed. I can add a group into domain admins and after a while they go away too. Now the users that are currently in the DA group remain without issue, but if you attempt to add someone they are removed. I have checked the restricted groups GPO and the domain admins are listed as a group, members say the same DA, and Member of is administrators. I have checked the permissions on AdminSDHolder CN on AD, and permissions match up to what MS says they should.
Can I get some other ideas on what to check?
Thank you,
Mike