Firmament Bug: Ice Cube Through Ground
I was attempting to put the ice cube back down so that I could ride the contraption through to the next area (the rock wall blocks it when the ice cube is attached.) Instead, I found that I could lower the ice cube through the ground. I didn't need to do anything special to get this to happen.
You can see if you look beneath the contraption that the ropes go right through the terrain. The puzzle is unsolvable like this, because eventually the contraption hits against a wall. I still don't know the intended solution, but this is surely not intentional.
This is a potential softlock because it's impossible to raise the ice cube back up through the terrain after it's been lowered like this. Thankfully I had a manual save from before I did this.