As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT THE GATE, STAB TRIM PERFORMED UNCOMMANDED FULL NOSE UP TO FULL NOSE DOWN MOVEMENT. STAB CH2 INOP STATUS MESSAGE APPEARED. DISCONNECTED STAB TRIM. STAB TRIM REENGAGED SEVERAL TIMES ON ITS OWN. INSTALLED SERVICEABLE HSTCU. OPS CHECKS OF STAB/YAW SYSTEM IAW 27-41-00. OPS CHECK GOOD.