o.o O..M..G...Really?!
See I didnt know that. I think then that should be another limit to.
One item to one collection. Because that would be crazy. To get one collection done, get that rare item in, and find out in the next collectio you need to collect the same item all over again.
Or at least, if you have already inserted that collected item in one collection, then it should show "collected" at least then in the other. Just if you put in one item, you would be able to remove just the one item.