Well, you are probably on the right track since I would assume that there is a potentiometer that might have a mis-aligned gear on the shaft that needs to be corrected.
Perhaps there are details in the manual about this?
http://bit.ly/1bnabX7It is a great game, so I wish you solve this issue.
By the way, I think that this question shouldn't be in the Monitor/video section, but that would be something that the admins could correct.