CBT Soap Fault from VMWare when runnnig Veeam backup

The error means that Veeam cannot identify what blocks have changed. This could have numerous causes, for example, your storage was powered down without to shut down the VMs via guest OS first.

The fix is fairly simple but it does require powercycling the VM, see KB:1113 - How to reset CBT. From the KB article:

1. Power off the VM
2. Right click the VM, click "Edit settings", find the "Options" tab and click "Configuration Parameters"
3. Set the "ctkEnabled" value to false
4. Set the "scsi0:x.ctkEnabled" value to false for each disk of the VM in question5. Open the source folder and remove any -CTK.VMDK files.
5. Power on the VM
6. Power off the VM again. This step is needed to update the CTK table.
7. Power on the VM
8. Rerun Backup or Replication job to re-enable CBT