incremental takes as long as full

[fslot]

Am testing Veeam. I created a forward incremental job with 10 file servers containing about 35TB of data. The full ran with no issues. I had set the incremental to run every 4 hours. The very first incremental that ran was fine for 9 of the 10, but 1 of them proceeded to run what appears to be another full. How do I troubleshoot?

[foggy]

How do you tell the tenth VM is running full backup? What kind of VM it is, does it have any existing snapshots?

[fslot]

The other 9 VMs ran incrementals of a few minutes each. The one in question was going on 6 hours and about a third of the way done when stopped it. 99% of the data on that server has not changed since the full.

[foggy]

The most effective way to identify the reasons would be contacting our support team. My initial guess was inability to use CBT for this VM for some reason (existing snapshots, for example).