We have the exact same issue as described here:
One of our motors is spinning visibly slower then the other three. This is also clear when we try to takeoff as the copter slides in the direction of the motor that is spinning slower.
We have tried recalibrating several times. Both auto and manual. We also changed the esc to control another motor and the same thing happened, it spins slower than the others so this is definately an ESC related problem. Unfortunately we do not have the equipment to test the pwm signal.
Who do we contact in order to get a replacement esc?