You can remove from one safe and add to another (as described above, in a very "safe" way, you have to go through "Add card" button in order to remove one). I have not seen any problems resulting from that. You can try having the card in both safes just as a matter of testing (you sort of are in unique position of being able to answer your own question and contribute to the knowledge here). If that does not work, you still have the option of keeping both cards in the same safe or moving one card to a separate safe.