Yeah, doors come open a lot, especially rear doors that pax don't close well. If you can reach it, you can close it by slowing waaayyyyy down. If you can't reach it, then you have to decide whether to land right away or continue to a better landing area. I've had 412 sliding doors come open, at least enough to get the light, and there you either yell at a passenger to close it, or if you're empty one of the pilots goes back and closes it. Having a door open isn't a big problem with most helicopters, because the airstream won't let it go out very far. But if you're an offshore ship, with life vests all over the place, you have to be careful that something doesn't get sucked out and into the tail rotor.