As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A FLIGHT TRAINING FLIGHT THE INSTRUCTOR SAID THEY WERE COMMING OUT OF A STALL AND THE ENGINE LOST POWER AND STOPPED RUNNING. AFTER LANDING, REMOVED COWL AND SPARK PLUGS NOTED THAT CYLINDERS 3 AND PISTONS MOVED AND CYLINDERS 1 AND 2 PISTONS DID NOT MOVE.