As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING A TEST FLIGHT THE RT ENGINE WAS SHUT DOWN AND THE PROP FEATHERED AS PART OF THE TEST FLIGHT PROCEDURE. THE FLIGHT CREW WAS UNABLE TO UNFEATHER THE PROPELLER. THE AIRCRAFT RETURNED TO THE AIRPORT AND LANDED SAFELY. UPON INVESTIGATION BY MAINTENANCE THE FEATHERING SOLENOID ON THE PROP GOVERNOR WAS FOUND TOBE AT FAULT. THE SOLENOID WAS REPLACED AND THE SYSTEM FUNCTION CHECKED SERVICEABLE.