Either way you are going to need to solder. I would swap motors from opposite corners. If the issue stays in the same corner, it is a FET/board issue. If the issue moves with the motor, it is a motor issue. If you got it stuck in a tree and applied throttle several times with the prop being obstructed, this will easily/quickly blow a FET or motor. Hope you get it fixed!
edit: All micro hobbyists are welcome in this forum! Toy and hobby grade alike.