So many maps connected...
Thing is with these kind of map packs, having a lot of maps connected to one another, a lot of maps will not work or will crash for people if they were to enter it.
It is a common map pack glitch and it's difficult to fix without restarting a map or remaking it somehow to become less of a laggy/object filled map.
That's the other reason, some maps are too full of objects and detailed things that it can become too much for a game to handle sometimes in a sense.
I hope this somewhat clears some things up for you, Black Cat~