I love this, I have no idea who is right. Here is my train of thought. The stepper moves the right distance, the conduit keeps it straight, but it’s the angle of the belt being pulled on. I spent a lot of time worrying about this during the original design but had no one to bounce this off of.
Think about it in a more extreme case. If the pulley was 100mm out of alignment and you were really close to the connection point on the corner block. Even though the stepper turned the correct amount it would be pulling on an almost vertical belt. It would move ever so slightly in the correct direction and the rest of the energy would be pulling in the vertical direction. Right? Or because this is a fixed system all that is being effected is the amount of force it takes to move?