YouE planetary motor is having problems how do I pinpoiont the problem? I was riding then I turned a corner went to turn the throttle suddenly it makes a loud grinding noise and is unable to accelerate.

I got the motor open and it can only start turning when I roll the motor backwards a bit first (forwards on the ground).

It rolls smoothly, planetary gears stay still till it makes a loud bang like something is catching then dead. It never takes longer than 10 seconds tops. At high speed the planetary gears move suddenly in a jerky motion but also the motor dies whenever there's too much of a jerky motion. 

Magnets are not loose or falling apart. There is no debris in the hub it is clean and well greased on the gear.

Can it be fixed? Any advice on how to make it work properly will be greatly appreciated.

[EDIT WITH NEW INFORMATION]

I disconnected the hall sensor to see if the motor would still function.

When I disconnect the 5 pin hall sensor plug the motor acts like a magnetic lock when I turn the throttle, it freezes the wheel in place. After a few seconds the controller stops feeding power to the motor. I can do it again once I reset the throttle and twist again. I am beginning to suspect the controller seeing how the hall effect sensors do emit information to make the motor time the controller to work properly when they are connected until the power fails with or without the sensors. The power fails at about the same amount of time per try.
The specs reads: max. 36 volts 
I switched over from SLA 36 volts to li-ion 42 volts. 
Some assured that it's within tolerance but I suspect that these Chinese controllers are also on the cheap side and aren't as robust to take on that much more above tolerance continuously. 

I got my new controller and now everything is back to the way it was. 
I got this controller:
http://www.ebay.ca/itm/36V-48V-350W-Electric-Bicycle-E-bike-Scooter-Brushless-DC-Motor-Controller-/172878396579?roken=cUgayN&amp;soutkn=IvO9vJ

I tested the throttle to make sure that it was giving the proper ohms. Check
I tested the magnets by short circuiting the 3 phase power for the motor a felt a turning resistance. Check
I bypassed the ignition and the brake switches, connected the throttle, then the 3 phase wires and connected the controller's self-learning wires and then the power. 

Before I was able to connect the hall sensors the motor was turning at about 1/4 power and I discovered that in learning mode it learns to know what direction to turn the wheel and gauges the throttle resistance. 

When the controller is powered and you disconnect then reconnect the learning mode wires while the motor is turning the motor will turn in the opposite direction. Also, in learning mode, if you turn the throttle the controller will learn to add more speed based on the change of resistance of the throttle. I went full throttle and it slowed the motor but another twist and it accelerated the motor. It figured out how it should react to it.

I hope this can be useful for those who need to figure out replacing a new controller.