I recently bought a drone from erlerobotics. I performed all the preflight tests and calibrations (Compass, IMU, ESC and RC). I made sure the rotation direction is correct. When i flew the drone it started yawing continuously. There is no mode that could stop it from yawing. I tried ALT_HOLD mode and STABILIZE mode since i do not have a GPS. The drone still yaws without stop.
I double checked the motors rotation and orientation, it's all according to the documentation.
Finally, i tested the drone on ground after removing the propellers and i found that one of the motors rotates slowly than the rest and sometimes stops rotation completely. I replaced that motor with the similar one on the other side of the drone (to make sure rotation is correct), and increased thrust slowly. The same thing happened with the replacement motor. Is this a problem with the ESC? I did not fly the drone before this happened (the yawing). Can you help me with this?