This is where it comes back around to not understanding the doors. I tried something that worked (and that I hadn't particularly thought to try before), but...if it has to do with the non-circled dots being "covered" by the red boxes, why does the door open in a2 even when nothing is near the dot in the south?
Meanwhile, I've just yanked the owl statue from b2 into a2, which has also turned it invisible, which feels like it's going to make this game so much harder now.