Hi Julian,
I would suggest editing your VM settings to use a "Static" MAC address. This way, when you move them the MAC shouldn't change. VMs should always be unclustered and then powered off safely before attempting to move them. If you skip either of those steps we expect there to be problems. For example, you will end up with a cluster out of sync situation, or worse.
You also mentioned the licensing. In the past (PAM 2.x), the license was invalidated if additional NICs were added or if the MAC Address of any of them changed. in PAM 3.x this restriction has been removed and you should be able to add NICs without harming the license.
More info on Additional NIC problem: Is it possible to add additional NIC cards to a vi - CA Knowledge
Regards,
Christian Lutz
Support Engineer
CA Technologies - North America