Ok, I was able to take a screenshot, but the problem is that I came at the wall from right in front of it. This defeats my idea that you can clip through from 3 tiles away. Also, I came through the wall on top of the chest.
Being serious, though, I wasn't able to reproduce the collision bug. I did change the Tilemap collider to polygon mode. While I'm hopeful that fixed the problem, I can't test it to be sure. Thanks again for the info!