For the past few months I’ve been using an in house script to manage the rebooting of Virtual Machines on Hyper-V hosts following Windows Updates. These Virtual Machines also take part in Hyper-V Replica Replication to a DR host. On occasion I’ve spotted that when shutting down (as part of the reboot sequence) the Hyper-V Replica state will go into a Error ‘Critical’ state.
As it transpires this happens when the machine is shutting down and Hyper-V replica is attempting to create a reference point to send replica data over to the DR host.
The best fix I have at the moment for this issue is to suspend replication (you can use the Suspend-VMReplication PowerShell Cmdlet as documented here – https://technet.microsoft.com/en-us/itpro/powershell/windows/hyper-v/suspend-vmreplication to accomplish this) before shutting down the machine and then resuming replication (Resume-VMReplication and https://technet.microsoft.com/en-us/itpro/powershell/windows/hyper-v/resume-vmreplication) once shutdown is complete.
You will also note this issue noted under Hyper-V-VMMS in Event Viewer with Event IDs along the lines of 19060, 33680, 32546 and 32026.