If there is nothing wrong with the integrated cutter, we can see if the material used is too thin or the thread is screwed incorrectly. If this is the case, you can increase the presser foot pressure and relax the pressure of the wire clamp on the packaging line. It should be noted that the moving parts of the machine should be checked frequently, and there should be no loose parts, otherwise there will be jumper wires and needles leading to insufficient hemming. It's just my opinion. I don't know if I can help you.