Might have to do with some kind of flag, the code does try to add 4 copies but it's probably limited to max 3. I tried adding a copy manually through console and it didn't work. I also tried adding other types of cards and with slut cards I can add up to 3 for girls I haven't beaten 2 bars for yet. (I was trying to get around the issue of having already upgraded the cafe before getting all Erika's cards)2 of ice should be a set of 4, I'll check the code if something is wrong with that.
Cafe cards is an oversight. I think I'll add locked cards as a reward for battles after upgrade.
Thanks for the heads up!
I can't find the code for actually gaining cards, but this might get you in the right direction?