I was playing around in Chamber 17, and I found a really weird bug / glitch. I’m sure you have already found it, but maybe not in this chamber.
It’s a bit difficult to explain, I suggest downloading the demo file I’ve made.
So if you do the glitch (Please forgive me, I don’t know it’s name) as you can see in Portal Done Pro-er in chamber 13 to jump into a area by using the edges of the portals (Edge-glitch? Sorry, not sure) in chamber 17, by launching a portal in the “hidden” / “clue” area at the ceiling and the other one at the entrance to the main area where you can jump on top of a cube, you get in a weird state, where the map is rotated 90 degrees, but if you cross a certain area of the map it changes back and forth.