Two weeks ago I noticed that the Hyper-V hosts from the cluster were loosing connectivity to the cluster and the virtual machines were rebooted. The most common event viewer log was “The cluster Resource Hosting Subsystem (RHS) process was terminated and will be restarted. This is typically associated with cluster health detection and recovery of a resource. Refer to the System event log to determine which resource and resource DLL is causing the issue.”
I started to troubleshoot the cluster and look for network issues between the hosts,hosts and storage, NIC drivers/firmware etc and everything was good.
In the end I found KB3192404 which is fixing the virtual machines (VMs) on a Hyper-V failover cluster that causes instability and crashes. So you better install this KB and make sure you keep the hosts patched and updated.