So I have a f450 Naza with the DJI 2212 motors with 3 lighting hobby 30a esc and 1 Quadkopters 30a esc.
Since few days I'm noticing that during arming the motors, the one connected to the QK esc sputters at startup and has a few seconds delay before spinning.
Today after 4-5 flights when I powered up the Quad and did the arming process sparks were seen from the motor and also smoke from it. I turned it off and inspected it, the motor was very hot and the esc was warmer as compared to the others. The motor wouldn't spin freely as others, it appeared jammed.
It seems that the motor has burnt off? Also has the esc been damaged as well since it was warmer than the others. I have a 600mw vtx power input from the same esc points if that's relevant.
Help will be appreciated. Thanx

Are you uing 3s or 4s battery?

3s 25c/50c 3300mAh

motor gone for sure.
Try for ESC with other motor ( do not connect for long... just try for 10sec)  ..... as per symptoms it looks ESC is fine .... the motor had problems.
Show pic of motor opened.... if you can remove the c clip.... you can rewind motor and use again.

Any help required ... let us know.

1. So now I took apart the motor and inspected, couldn't find anything. The motor doesn't spin as freely as others normally and on connecting to other escs it didn't spin, just sputtered and smoke came out again.  

2. The esc connected to the problematic motor is dead, It wouldn't beep on power up and doesn't give power to any motor connected to it. It gets super hot.

3. Another issue which came up this morning was that after arming, the 2 forward motors would start spinning but the 3rd Motor (acc to Naza) wouldn't spin unless I raised the throttle and when I raised the throttle this is what happens:
ARM - Forward 2 motors start spinning, 3rd motor not spinning, 4th is excluded.
Throttle 20% - 3rd motor sputters
Throttle 30-50% - 3rd motor spins but at a speed slower than others.
Throttle 50-70% - Motors 1 and 2 rpm increase, 3rd motor spinning at same speed as it was at 50% throttle
Throttle 70-100% - Motors 1 and 2 spinning at full capacity, 3rd motor stops spinning.

ESC OUT OF SYNC? SUDDENLY?
WHAT THE HELL IS GOING ON HERE!?