I would first check to see if your battery is sufficent for the motor draw. It could be the motor is drawing down the pack enough that the esc is sensing a low volt condition and is trying to shut down.

If the bec is getting hot, either you don't have enough airflow over it, or your servos are pulling the max the bec is rated for.

As for the glitching servo, could be quite a few things. Like a defective servo, which may be contributing to problem above. Try swaping the servos around to see if it's a bad servo or a channel related problem.

Rx interference, antenna running to close to the servo/esc/bec/motor wires.

Any carbon fiber in the plane? Can cause interference problems too.