I've experienced a similar issue before, but I only thought it was in one location, and I ended up still inside the map. Where exactly were you able to escape the map?
after killing the priest, climb up passage (now roof) with a way to the left
I wasn't sure where exactly you were referring to at first, but I finally found it! It's the spot in the picture below, right?
Looking at it again in my editor, I'm pretty obviously missing a collision box there... Oops! I will fix this in the next update. Thanks for the bug report!