Thank you both for the responses. Sorry, been off for a couple of days so haven’t responded.
Status of VSS Writers appears to be fine. They all have a ‘Stable’ state and ‘No error’
After comparing the VeeamGuestIndexer log in the above directory on the affected system and another system that’s working, I can see the point where it fails.
Guest file indexing has been enabled. App-aware processing is NOT enabled.
This is a VM backup of multiple VM’s. Error has only started since enabling Guest Indexing (for malware detection) after upgrading to V12. But the strange thing is it only affects this single VM - all other VM’s, including the one I compared it to, are carrying out the indexing successfully. So definitely appears to be something specific to this VM. It’s a Win Server 2016 (as was the one I compared it to)