KB1377: VSS wait timeout - Veeam Software
https://www.veeam.com/kb137702.12.2011 · "VSSControl: Failed to freeze guest, wait timeout" Refers to the limit imposed by Microsoft VSS writers on the duration of a freeze. This timeout is not configurable. Veeam uses VSS to freeze applications immediately prior to creating the VMware snapshot, and then sends the thaw command as soon as snapshot creation is complete.