As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRIMARY TRIM WOULD NOT OPERATE IN NOSE UP POSITION WITH YOKE SWITCHES, FUNCTIONED PROPERLY FROM SUITCASE HANDLES. FLIGHT RETURNED TO DTW AND LANDED WITHOUT INCIDENT. OPERATIONAL CHECK WAS NORMAL ON GROUND. DISCREPANCY COULD NOT BE DUPLICATED, AIRCRAFT RETURNED TO SERVICE.