As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE USING SPEED BRAKES IN IMC CONDITION, PILOT REPORTED AIRCRAFT MADE HARD LEFT TURN. IT WAS LATER DETERMINED THE RETURN SPRING DID NOT ALLOW THE SPEED BRAKE IN ONE WING TO FULLY RETRACT CAUSING THE TURN SITUATION. THE RETURN SPRING WAS BROKEN AND WOULD NOT ALLOW SPEED BRAKE RETRACTION (TO OFF, CLOSED POSITION) UNDER AIR-LOAD WITHOUT SPRING.