As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT PORPOISING IN CRUISE, VIBRATION IN CABIN FLOOR, AND KNOCKING SOUND IN REAR. FLIGHT DECLARED AN EMERGENCY AS A PRECAUTION BUT LANDED AT MSP WITHOUT INCIDENT. MAINTENANCE FOUND FOLLOW-UP BALANCE LINKAGE BEARINGS TO RIGHT ELEVATOR CONTROL TAB BINDING. REPLACED FOLLOW-UP BALANCE LINKAGE BEARINGS AND RERIGGED TRIM. OPERATIONAL CHECK OK. AIRCRAFT RETURNED TO SERVICE.