As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB/CRUISE PHASES OF FLT A LOUD BANG/THUD SOUND WAS NOTED. IT APPEARED TO COME FROM FLOOR BELOW BOTH PILOTS SEATS SIMULTANEOUSLY AND BOTH CONTROL YOKES JERKED. EVENT OCCURED THREE TIMES DURING FLT. R&R ELEVATOR SERVO IAW AMM 22-11-04. A/P FUNC CHECK GOOD AT THIS TIME OK FOR SERVICE.