As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOI - FLIGHT NR 2398 DURING CLIMB NR 2 PROP CHANGED FROM 850 TO 1020 UNCOMMANDED, POWER LEVERS IN RATING DETENT. CONDITION LEVERS AT 850 POWER AT MCL. AFTER RESETTING PROPS TO 850, -5 MINUTES LATER NR 2 PROP AGAIN WENT TO 1020. REPLACED PEC, OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.