I think you mean Hall Sensors
(not MOSFETs) and there are three of those in the motor.
The Hall sensor in the throttle is linear and gives a variable output according to the throttle postion, whereas the Hall Sensors in the motor are latched and simply switch between high and low output
Honeywell SS41 Hall Sensors are the ones commonly used as replacements inside the hub motor.
I'm not convinced it's a Hall Sensor problem because the MPII controller should still work in sensorless mode if the Hall Sensors fail. When a Hall Sensor fault occurs, the motor usually works once the bike is moving, but will not work from stationary.
If it's been impacted from the side, it's more likely that the wiring harness
(or the molded connector block) has sustained some internal damage.
When the motor stops, try wriggling the wiring to see if it starts to run again
When the hub cuts out, are the battery gauge lights still lit up? as is might be a battery problem rather than the motor/controller.
