Virtual Machine is 'corrupted'

I'd like to know why Paralleles (5) is so picky about using a copied/moved Virtual Machine. I run my VM on a laptop when on the road and on a desktop when at home. I copy the VM using rsync from one to the other.

When I get the 'corrupted' warning on starting the VM, I can do the following:
1. rename the parent directory of the VM
2. double click the VM
3. Parallels asks if the machine has been moved or copied
4. I say "copy" (did not test "move", but that was probably smarter)
5. It gets renamed in the VM list
6. It just works

So, not so much the VM is corrupted (as Parallels says) but Parallels itself checks for things which are unnecessary.

I'd like to know how to prevent this load of actions I have to perform after every copy.