These double-sized boxes in the transition area have a bad texture offset, making it look like they're cut off.
More double-sized boxes out in the open; the fact that there are several of them next to each other partially covers up the flaw, but they still get cut off at the edges.
In orientations 3 and 6, the "exit hole" is vertically shorter than it is in the others, which may lead to the player getting unduly rejected while trying to go in.
Get up to this point in orientation 5 (everything inverted), then go forward and left...
It's a gap! You can break out of the map, but can't do anything relevant there--the checkpoints are thankfully out of reach from the outside.