Posted by Changed block tracking information is no longer being read, causing entire disks to be read instead of just the changed blocks.
This is a very generic error, so it is quite difficult to say what has happened.
Hyper-v Solution:
Run “sc stop veeamfct” and “sc start veeamfct” on the Hyper-V hosts affected to restart the Veeam Change Tracking service, and then see if the errors are resolved afterwards.
VEEAM KB1881
OR
When you run VEEAM V8, you must install patch 1. After this update the Flush change tracking data errors are gone.
This patch can be downloaded from the here:
VEEAM KB1982