On a educational, unlicensed, machine, we just ugpraded to 7.3 and since I came from 6.5, I've choosen a blank install, introduce old SR with VMs and metadata-backup (getting all back is a bit of work, but in the end it worked!).
When I tried to move VM-disks back to the OS-SSD, it tells me that I'm unlicensed and simultaneous moves and live migrations are only possible with licensed version.
Since neither the VM is running, nor any other move was in progress (xe task-list...), there's obviously something broken.
Only working way: detach, move, re-attach.