Trial of Chaos did not spawn power stones

I was just attempting the trial of chaos (again) and was doing pretty well, until I entered an area where I'm supposed to collect 3 chaos power stones to place in altars. I cleared all of the monsters and the area was a river bank with a lever in the middle. Pulling the lever closed the left (western) area off and opened the northern one. I killed the monsters that were in there, and explored the small dead end that was present.

I pulled the lever once more and the north closed, and west opened. I killed the monsters in there and again looked around the small dead-end area. Nothing. The map suggested that there must have been a space to the north west but it was unreachable. There was no other lever to pull anywhere on the map.

Same problem happened to me in a trial with the same layout as yours.
Bug Report ID: #2005708297

EDIT: Didn't figure we could get back on the elevator that took us down in the pit. You can walk on the walls that you raise with the switches. No bug.