Issue with "Cryptographic Services" and backing up a VM.

Good Afternoon,

I'm having problems with the backup on one of our Hyper-V hosts. We use Veeam B&R to back up all the VM's and I have a problem with one VM in particular which doesn't backup, the VM is 2012r2 Essentials. 
The windows backup on the hyper-v host also doesn't work backing up this VM so I know this a Microsoft Windows Issue rather than a Veeam issue I guess but just wondered if anyone has come across this problem?

After troubleshooting all the VSS writer issues and Event ID’s I've narrowed down the problem to one VSS writer inside the problem VM:
‘System Writer’ state: [8] Failed Last Error: Inconsistent Shadow copy. is the error inside the VM every time the host backup runs.

I restart the “Cryptographic Services” which makes the VSS writer stable again but when the back runs on the host it causes a failed state again.

When I run Windows backup inside the VM it backs up fine!

Now if I stop the “Cryptographic Services” service on the VM and run the Hyper-V host backup it completes without issue! so definitely points to this service/VSS writer.

So my problem is the “Cryptographic Services” causing the failed backups. I think the service itself is fine but maybe a corrupt VSS ‘System writer’?
if so what is the best way to fix just this writer? Re-Register the DLL’s? if so does anyone know the correct DLL’s to re-register? I tried the generic DLL's from google related the VSS but makes no odds.

All servers are patched and up to date. I've done several reboots, and SFC has been run inside the VM. also done the usual Chkdsk etc.

the VM is 2012R2 Essentials -No SQL, No Exchange on this VM. all the other VM's backup without issue.

Any help would be greatly appreciated!