Windows Server 2012 R2 Hyper-V: Several VMs stuck in saved state after host graceful reboot

A Hyper-v host running Windows Server 2012 R2 Datacenter auto-rebooted (gracefully) after installing updates (will address that later).
After the host came back online, three VMs are stuck in a saved state and give the attached error when trying to start.
Anticipating a multi-part approach here, so wondering what the troubleshooting steps would be...
Thanks in advance....
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Cliff GaliherCommented:
This happens when a physical disk is not available. Such as a USB disk configured for passthrough. Pretty common when a USB drive is unplugged and a VM is running. The VM stays running until a reboot.
redgobletAuthor Commented:
Thanks Cliff...a subsequent reboot did not fix the issue; the VMs are still stuck in the saved state.
At first, I was worried that one of the VMs (which has 168 GB RAM assigned to it) may have been unable to save its session state and it caused a cascade failure of the other by hogging whatever temp storage was being used for same.

Any recommended approaches from here?
Cliff GaliherCommented:
The error when you attempt to start a VM tells you which file/path is the problem. Make sure the disk is attached and the file is accessible. That's a start. As my previous reply stated, this is a file issue, so it is not surprising that a reboot didn't fix the issue. I never implied that it would.
redgobletAuthor Commented:

I have verified the paths to each VM resource (vhdx, config files etc) and can reach them from the host. Some of my reading suggests a permission issue that may have arisen...though some VMs located within the same directories are working fine.
Cliff GaliherCommented:
As I said, look at the path *specifically* in the error message. You van configure a VM to save its state to a different disk, for example. I see this often with USB dives and external SAN storage. If the saved state is on an iSCSI disk that didn't remount, the VM will fail to start. Just looking generically at the config file and VHDX does not give a complete picture. That path and file is in the error for a reason.

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Windows Server 2012

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