Greetings, Electrics are not my Bag but I'm an electronic Tech so...
For the shutdown:
1) What is the voltage / Wattage / cell # rating on the speed control?
2) Did the speed control and motor come in the kit or did you get them seperate?
3) Does your Battery pack match the speed control for # of cells or Voltage?
4) Does the Motor Rating match the speed control rating?
5) It there any way you can attach a heat sink < cooling fins> to the speed control?
Possible shutdown / overload causes:
1) Pitch of the main blades set too high? This will cause the motor to work hard at low speed and draw to much current.
2) Drag in any rotating parts? Excess drag will cause more current draw.
3) Any added weight in the kit? Oversize batterys or motor can be heavier than the design allows. Any extra's added for any reason can make the bird too heavy. Weight is not your friend.

Good Luck.

Ramjet