As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ON APPROACH TO PHL, CREW REPORTED A FLAP FAIL CAUTION MESSAGE WHEN THE FLAP HANDLE WAS MOVED TO 30 DEGREES. FLAPS WERE STUCK AT 20 DEGREES. CREW LANDED IN PHL WITHOUT FURTHER INCIDENT. MAINTENANCE TROUBLESHOT THE AIRCRAFT, REMOVED AND REPLACED THE SKEW DETECTION UNIT (SDU) AND PERFORMED CHECKS USING THE AIRCRAFT MAINTENANCE MANUALS. AIRCRAFT WAS RELEASED FOR SERVICE.