Check the substrate infeed sensor.....
Unload any media in the machine. Get flashlight, get on knees, look under infeed assembly, as if you were looking up from the floor. You want to look about 12" to the left of the right side of the feed area. You will see a stamped out area of the sheet metal, to which a black plastic media presence sensor is attached. It's a pivoting lever type sensor. That might be bent, broken, or sticky. You can actuate it manually with a small screwdriver and see if that fixes your error. Unloading a heavy media or fabric too quickly can result in distorting or damaging it.....guess how I know.