I should also have said (between #1 and #2) that anything touching the mat on the "C" side would cause the behavior as well.
And, that I believe that a defective "C" motor is unlikely - only mentioned because it is possible.
What does your drive train look like (simple wheels, simple treads, or a complex mechanism) and what contact with the mat is there besides the drive mechanism.
One year the team didn't do a good job of setting the height of attachments (or initial placement), so they dragged a lot, but with no constancy. As a result, they never knew which way the robot would go because the controller frequently couldn't compensate (and they had a pretty simple drive mechanism) - they ran into alot of stuff and subsequently didn't score well.
Brian
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