Possible Bug/Glitch? (SPOILERS)

[CypressDahlia]

I managed to get through the Control Room area of the game by solving only two puzzles (the weight and levers), instead of three. I have the non-patched, original release version of the game and am running on Win 7 64-bit, just in case you needed that info.

I got through this area without having to assemble the pipes. What I did was solve the first two puzzles, drain the sewer, come back and solve the second (lever) puzzle a second time and managed to get the progress event (where the valve on the median door breaks). It was strange because the controls on the first puzzle lock after you get it right whereas the controls on the second puzzle do not, therefore it's possible to solve it twice, but it registers as having three puzzles solved in total thus allowing you to skip the pipes.