v6 HotEnd Full Kit - 1.75mm Universal (Direct) (12v) I have run M303, PID Autotune, and changed the firmware. However, the problem is that the hotend cannot maintain the correct temperature. I have changed the Heater Cartridge. I have changed the NTC thermistor, I even tried the new Block & Sock - V6 Upgrade kit with the cartridge thermistor. But still will not hold the temperature.