Hyper-V virtual machines hanging (presumably after SEP 14 update)

I don't have 100% proof, but we recently started experiencing some VM servers hanging (it seems to be working, but one can't logon interactively to them and WMI scanner reports connectivity errors). The only change recently was installing of SEP 14 MP1 client (Basic Protection for Servers) over the latest 12 version. Currently i had two 2012R2 servers hanging once per week (they are on the 2012R2 host which also received SEP 14). And one WS2008R2 which is hanging every few days, which is on WS2012 Hyper-V host with SEP 12 for now (VM is on SEP 14). I don't see anything in the Event log. These machines were running smoothly for half a year with SEP 12.