On 99 out of 100 brands of plotters there is a y axis tab on the pinch rollers that interacts with an electric eye on the blade assembly that rides back and forth on the transom(extrusion and or rods the blade assembly rides upon). this is to tell the machine the "Y" limits of the vinyl you have inserted into and under the pinch wheels,so to keep the knife cutting on the vinyl only,(this is why the machine never cuts past or beyond the pinch wheel locations)..if you have an alarm going off on that axis the first thing to check is the pinch wheel location,...secondly check to see if any debris is interfering with the sensor or electric eye on the blades assembly(it may simply need cleaning with some q-tips and alcohol,check your manual or the support site to be sure about this). next it might possibly be a bad sensor or electric eye which will need to be replaced by a trained pro. the list gets worse from here,....