I don't recall if I reported this before and it's kind of fun, so it might be nice to leave, but: if you drop down a chute and escape to the next floor fast enough, the allies that would've followed you down the chute appear after a time delay at your entrance to the next map, instead.
I noticed this a while ago, it might've even been in beta 7 and it's possible it was fixed since then, I don't see any other reports of it here though.