"DvmFSIncomplete" error while attaching to an existing repository


We are receiving a "DvmFSIncomplete" erorr while attempting to attach a copy of an existing repository to a new core installation (full DR test)

Here is the stack trace of the error:

Server side:

Replay.Core.Contracts.DedupeVolumeManager.DedupeVolumeManagerException: File system is incomplete

Error checking the file system: '50e0190e-ddd3-45b3-8cf1-efae9e549cf1', data path: '\nas01.mydomain.local\RapidRecoveryLive', metadata path: '\nas01.mydomain.local\RapidRecoveryLive' - Error(s) 'DvmFSIncomplete' at Replay.Core.Implementation.DedupeVolumeManager.Dvm.<>cDisplayClass46_0.b0() at System.Threading.Tasks.Task.Execute()

Not sure if this could have an impact, but the new core install is at 6.5 while the repository was connected to a core running version 6.4. 
I've made sure the filesystem is not readonly.
I've looked through the KB but could not find any reference to the error in question.
Any ideas?