The printer is designed for one size of roller. The outter rollers are tapered and should be installed with the dot to the outside. The inner rollers are flat, so there is no orientation issue there. Get new rollers, clean the grit wheels and load a roll of media.
Here's how I test this - place a piece of masking tape under the edge of the media. Mark the edge of the media on the masking tape and place a line 90 degrees (you'll make a plus sign "+') so you know the feed position of the vinyl. Feed out 10 feet or so and slew it back in till you have the media at your starting position. If the edge of the vinyl is at your mark when you return to the starting position, the pinch wheels are pulling straight. Now, if it is pulling straight and you still have problems, check for how you load your media.
I've also seen too much pressure on the knife cause tracking issues. People won't expose enough blade and try to compensate by increasing force, but this only acts like a brake on the vinyl.
I hope this helps you figure it out.
Good Luck,
