Error Code 6398 - Critical

Question

This error code keeps showing up and now Active Directory users can no longer edit documents etc., on SharePoint! Please Help!

Answer 1

I would suggest you do the following in that order:

1. You might find more information by checking timer job history under Monitoring in Central Administration.
2. Check ULS logs.
3. Stop-Start User Profile/Synchronization Service.
4. Reprovision User Profile Service via PowerShell.

If that doesn't help and you don't find the cause of the issue, you could recreate the User Profile Service Application. There is a really useful guide on that: http://www.harbar.net/articles/sp2010ups.aspx . It's for SharePoint 2010, but there isn't a big difference between 2013. Fixing User Profile Service can sometimes be a real pain.