Did you ever reduce the throttle and fly it without having the stick full forward?

One thing we teach when working with a student is throttle control. Take off at full, then reduce the throttle to a point where the plane will fly without full, then adjust trim of the elevator and any other control so that you can fly straight and level with hands off the transmitter.

Operating an electric at full throttle all the time does two things: it will run the battery down post haste, and it will put an unnecessary load on the motor. It does not need to be run at wide open all the time, in fact, that is pretty much not the way you should fly.

That could have contributed to the engine seizing up like that, simply from overheating from running it under full load for pretty much 100% of your flight time.

CGr.