A few years back, I owned an SC machine. It was manufactured with the set-screw on the back rail in the wrong position, so that when sliding the pinch-roller assembly over to hit that stopper, the rubber wheel would not be in contact with the lower grit roller.
At the time, I created a thread here about this issue, and also called it to the attention of USCUTTER so they could contact their people in China and have factory engineers fix the problem.
Well, guess what? Today I got their Brand New Improved SC2, and it has this same defect. I kid you not.
So, I took out my electric drill, made a new hole (1.25" over) and put the screw in position where it belongs. Now, when the roller assembly is moved over to that stopper, the wheel remains in contact with the grit roller up front.
Anyone who owns the SC2 should be aware of this, because if you slide the right-hand spring-loaded wheel all the way over to the end of the rail where the factory places the screw, it won't hold your vinyl properly and it'll scrunch up or not feed properly.
And so it goes...