You have to get that fixed first, before you start cutting designs. The corners have to be square. Work on the blade offset. Or contact tech support. Make sure there is nothing in the blade holder, make sure the blade is spinning freely. A drop of sewing machine oil or other light oil.. Make sure the white wheels of the carriage head are firmly down in the track. Make sure blade tip is not broken.
Also those track marks don't hurt a thing. they will come out when you apply the vinyl. I hope you didn't loosen up the pinch rollers to try and get rid of the track marks. That will cause you more problems messing with the pinch rollers. The vinyl won't track right and start slipping.