We are a Windchill 10.0 M030 Setup featuring a 4 node Microsoft Cluster running SQL and on top of that, all virtual. This is what we have learned during an exhausting week recently of sporadic downtimes and headaches. ALL of my data comes from Microsoft themselves, here.
Our servers belong to many groups and this was the fix. A real head scratcher folks. It also remedied an issue where we would receive an email about a vault being offline due to loss of communication.