You can get to the screws that mount the barrel from inside once you pull the turret ring.

Before anything, double check the connection for the recoil at the MFU. That one is in the corner and you should make sure one of the leads didn't slip out of the jst housing. For some reason, my recoil connector on the JS-2 likes to pop a wire.

It's probably not serious, these things are pretty hardy. Mine got jammed by being knocked off a table and landing on the barrel. It twisted the metal frame of the recoil unit. Bent it back and all was fine. When you get it out, first check around the microswitch to make sure it's in position and free, then check barrel alignment, obstructions. If everything's okay, pop the plastic gear cover and have a look that everything is in place. You can pop the motor then a bench test it.

Worse case scenario, you can buy a new unit from Jason for about $40.