As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FINAL APPROACH WITH AUTOFEATHER SWITCH ON, LEFT PROP SEEMED TO FEATHER. TORQUE JUMPED FROM 25 PERCENT TO 75 PERCENT AND NP DROPPED TO APPROX 38 PERCENT. CLEANED COUPLING ON LEFT TORQUE SIGNAL CONDITIONER. OPERATIONAL CHECKS GOOD. COULD NOT DUPLICATE DISCREPANCY.