vmware.log
file of the affected virtual machine, you see entries like this:XXXX-03-08T04:10:09.790Z| vmx| SnapshotVMXTakeSnapshotComplete done with snapshot 'test4': 0
XXXX-03-08T04:10:09.790Z| vmx| SnapshotVMXTakeSnapshotComplete: Snapshot 0 failed: Failed to quiesce the virtual machine. (40).
XXXX-07-01T15:30:43.244Z| vmx| ToolsBackup: not enough empty nodes (needed 9, found 6)
To resolve this issue:
Alternatively, for virtual machines with more than 7 disks on a single SCSI controller, instead of creating a new thin disk and adding this to a new SCSI controller (SCSI1:0):