Over the last 6 years I ran only into 2 scenarios that leaded to problems:
1) Some older versions of legacy backup vendor software (BEX) added some special stuff into VSS framework and our InGuest processing (and VMware Tools quiescense) was not able to use VSS without errors. I never came across this problem in the last 2 years anymore.
2) When you run another Tape backup software on the same system were our Tape Server roles is installed, the other software was not able to use the tape drives anymore as we "consume" all tape drives that windows see. => Use another server for Veeam as Tape Server.