Not all Windows applications are VSS aware.
Some will crash when a VSS snapshot of the VM is taken, others just don't quiesce and won't be transactional consistent.
We have two such applications out of a catalogue of five hundred applications.
Know your service catalogue and test the outliers outside production environment.
Microsoft, NetApp, Symantec, Veeam, Veritas and VMware certified professional
MCTS, MCSE, NCDA, NCIE-BR, ASC, SCS, VMTSP, VTS, VCP