It's the "Powerbox Sensor Switch" I think it needs to be stuck together inside, if I got another one I would take it apart and fill the gap between the boards with 30min epoxy, that should hold it together if there is excessive vibration.
I did have a problem with the engine to start with which broke 2 of it's mounting lugs, it was an SPE 40cc gas.
I think this vibration has caused the switch to fail, though it should fail safe, unless it will only do that if one of the components inside goes down and not actually come apart, it was a good switch till this happend, gave me 5.9 volts and 5 amp to the servos with 2 Lipos
running together, if one fails you still have power.
Don't want to put you off using one.