If that's the place I think it is (the very end of the level in the submission page image), there's actually a neat trick to get behind the crate that even I wasn't aware of until just now, because I made a last-second change to fix a different issue and accidentally added a final trick to that level. As it turns out, elevators can be useful even if you don't actually change floors with them.
I was pretty short on time, so that's the last level anyway, and you pretty much solved all the puzzles that were intentionally in the game.