Microsoft/IBM Hyper-V cluster- Migration between nodes fails for all VM's

I have a 2-node Hyper-V cluster running Server 2012 on identical hardware with a FC-connected MPIO SAN, all of it IBM hardware- 2x 3650 M4's and a Storwize v3700. This has been working for about 5 or 6 years now without incident. Recently, one of the node stopped running VM's- the machines simply will not start up on this server. When I right-click the failed migration attempt and click "information details" I get a 0x80004005 error that says
"The migration failed at the destination. The processor settings for the virtual machine are not compatible with your physical computer 'HYPERVISOR2'. To migrate this virtual machine, you must first shut it down...."

Then it follows with instructions on how to transfer the machine to the other hypervisor that failed the first time. I have followed these steps, but given that the two hypervisors are identical, got the expected result: The same error message. I set the checkbox on the VM for processor compatibility mode, and got the same error. Doing a migration to the second hypervisor succeeded, but the VM gave me the same error when I tried to start it as well. I evicted the node from the cluster and added it back again (I can't use it because all the VM's have this problem anyway). I had run the Cluster validation wizard, and it had a few warnings, but they were for VM's that are powered off pending decommissioning. I did not make any changes to the configuration of either cluster member. All the networks match and work, and both nodes have access to the CSV. I really don't want to rebuild this node- Any ideas?