Hello. I've been working on a DIY drone for a while now. It has gotten so far that today I was going to calibrate the PID-constants. While working on it I discovered a major problem. 3 of the 4 motors works as desired, but the forth won't. It worked with the same code that it runs now. The ESCs seems to be working on all of the four motors, there is the twitching when powering up. But then nothing happens on that motor. If the ESC recieves over about 1500 it starts spinning at a lower speed then the others. The motors are DYS BE1806 2300kV and the ESCs are DYS 20 amp. The drone is powered by a 3s 2200mAh battery. Im greatful for answeres and am happy to explain in more detail if required.