KB1934: Hyper-V Changed Block Tracking Troubleshooting
https://www.veeam.com/kb193430.09.2014 · How to manually reset Veeam CBT Should the information above not resolve the issue, changed block tracking can be reset for a Hyper-V cluster by performing the following steps: Right-click on each host in the cluster, select Manage Volumes and then tick the box to " Disable changed block tracking for this host (not recommended) "