Control room - I caannot find 3 pipes.

[Dongra]

I had this issue as well. When I was first in the control room I didn't know that the pipes were a part of a puzzle until after I had completed all the other puzzles in the area. I think while I was in one of the rooms I found one of the pipes and moved it because it was in my way and it must have fallen through the floor without my knowledge. I spent hours trying to find the final pipe, thinking that it was possibly well hidden and even climbed up pipes to get towards the ceiling to search for a very clever spot, but I eventually loaded the game and found all of the pipes in their correct locations.