As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT ELEVATOR TRIM IS LOCKED AT 4.5 DEGREES. FLIGHT RETURNED TO DEN. *S/D* INITIAL EVALUATION DID NOT UNCOVER ANY FAULT MESSAGES RELATED TO THE AIRPLANES STABILIZER OR FLIGHT CONTROLS. MAINTENANCE ACCOMPLISHED PRIMARY FLIGHT COMPUTER TESTS, ACTUATOR CONFIDENCE TESTS AND STABILIZER SYSTEM TESTS. ALL TEST RESULTS WERE NORMAL. ROOT CAUSE IS UNDER REVIEW BY UNITED AND BOEING ENGINEERING.