Is it possible that, for example, if you make a func_door, and it would open to the void (but while closed, it's sealed completely from leaks) would it cause a leak error?
Say you have a U, in the middle of the U is the door, and it's closed in by a room. Therefore the door in the middle of the U is sealed from leaks. But when the door opens upward, it penetrates the outer perimeter of the room, causing the door to open into the void.
I haven't had a problem like this before, so I don't think it does cause a leak as I have explained, but I've spent hours looking for leaks in my map and can't find any!