SP2013 - User Profile Service, Corrupt?

Question

SP2013 Two Tier Farm. A Little bit of an outage this morning which caused a few VM's to drop storage. Had to restore storage and bring servers back online.

SP came back up fine, however; ever since then, the User Profile Service has been unhappy. It won't complete a sync, incremental or full.

Event viewer is full of error messages relating to "FIMSyncronizationService ERROR"

Brief text from event viewer error:

The extensible extension returned an unsupported error. The stack trace is:

"System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.AggregateException: One or more errors occurred. ---> Microsoft.Office.Server.UserProfiles.UserProfileException: Exception while trying to migrate account 'DOMAINNAME\USERNAME' to 'LONGERDOMAINNAME\USERNAME'. ---> Microsoft.SharePoint.SPException: The user does not exist or is not unique. ---> System.Runtime.InteropServices.COMException: The user does not exist or is not unique.0x81020054

I have tried all of the basics:

1. Rebooting
2. Deleting and restoring AD Sync Connection
3. Running full search crawl of the mysites
4. I did all the above again but via Powershell.

My next step is to "nuke" the UPS App and nuke mysites, to rebuild it again. But that'd be a days work and downtime, not ideal.

Answer 1

Please check this article: https://thomasverwer.com/2015/07/24/sharepoint-user-profile-service-application-exception-while-trying-to-migrate-account-the-user-does-not-exist-or-is-not-unique/, worked for me.

Answer 2

I ended up having to nuke and re-build the user profile service and MySites as well. It was all corrupt. It was essentially like starting from scratch again.

Just answering my own question in case someone else finds this thread.