Domain Controller Problems

I have a problem that my company has inherited from a client's previous IT Director. We don't have nearly enough information on the situation but are working with what we have been able to decipher from his notes.

We were having an issue with an old domain controller. It is no longer the primary domain controller, but it is still playing some roles in the network. Trying to get a snapshot of it in VSphere someone took the server down. This caused some DNS problems with Sharepoint, the print server, and caused some permissions issues with some shared drives. The person who took it down was able to make a new machine and load an old backup. A backup from September, I know, shitty situation but also inherited from former IT Director. Anyways, it appears that this DC hasn't synced with the primary domain controller or either of the other backup domain controllers since a few weeks before this backup.

Since the virtual server of the backup was stood up we continue to see problems with Sharepoint permissions, some shared drives permissions, and we continue to get domain trust problems on many people's computers. I also appear to be seeing problems with Group Policy updates on many user's machines.

I know this isn't much information to go off of but I was hoping this might be able to jump start s discussion that could lead me in the right direction with what to do.

I was thinking of removing the problematic dc altogether and setting up a different server for the shared drives that were running on it. So I would then go to the servers that are pointing to it and change the dns servers they look at in the network settings. I'm not sure what to do about the rights issues however. I assume the shared drive problems will clear as i set everything up on the new file server, but my problems with Sharepoint and the domain trust issues I am seeing I am not sure what to do with.