This video depicts a bench test where a quadcopter with Turnigy Multistar 4822 690Kv motors and Afro 30A ESCs stalls at various throttle settings.
This is a known issue with current SimonK firmware (that ships with the Afro ESCs) and high pole count "pancake" motors, where sync is lost due to the dynamics of the high torque motors.
Stalls happens at any throttle setting but tend to happen more frequently above 30%. Dropping the throttle to 20% or so helps the ESC sync again with the motor.
At this point SimonK firmware is a good choice for lower pole motors (ie, motors with higher Kv rating) but you should avoid it for heavier designs.
This kind of bench testing is dangerous. Please use extreme caution when doing this at your own shop, stay clear of the multirotor and wear eye protection.
See http://bit.ly/1vYgjjN and http://bit.ly/1LwFkGK for more detailed discussion
