Ok, so I repeated the glitch but sadly, before I could take a screenshot, it became nightime and I was sent back to my house. I think If you stand 3 blocks back from the wall, there is a chance that you can clip through the wall.
Thanks for the information. I'm still not able to reproduce the bug. (I believe that it is happening! It's just hard to replicate these things sometime.) You mentioned that you were standing about three blocks south of the top wall - about where were you standing in the east / west direction?
I've gone ahead and changed Unity's Tilemap collider from "outline" mode to "polygon" mode. This'll get pushed out in the next update (today or tomorrow). I think this will solve the issue, but I'd like to reproduce the bug first so I can prove it. I do appreciate the bug report and the help :)