And even more info, after pausing both VMs, I simply created a copy of the VMDK file. Then I removed the original VMDK from the guest, restarted it to make sure everything is cleaned, and added the copy as a shared disk, with this result:
Failed to lock the file
Cannot open the disk '<path>\Virtual Machines\VMware\Shared Disks\<file name> - Copy.vmdk' or one of the snapshot disks it depends on.
Failed to power on 'scsi0:1'.
Failed to add disk 'scsi0:1'.
Could not add device scsi0:1.
Still don't see why one of the VMs is looking for a snapshot of a shared disk. Or is it looking for its own snapshot, corrupted during the host crash?