Editing with a little bit more detail and gonn' bump this bug up a bit.
https://image.prntscr.com/image/7toh_X9HQyaNI3LMfDWKfA.png
So when a player is standing in the lower half between these two gates while the right gate is closed, this messes with how the two lumbers spawn in the second(?) wave in this area, causing one of the lumbers to spawn on the opposite side of the one-way gate, making it impossible to advance in the level. I originally made this post months after the bug happened to us so I didn't have good memory of it, or any screenshots, but we have managed to get it to happen again.
These circumstances probably aren't too common, but the chances of it happening to other players as well might just become a very minor annoyance, forcing players to restart on a run.