"DvmFSIncomplete" error while attaching to an existing repository

Hello, 

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?
Thanks
DanT