As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WHILE AT THE GATE, STAB TRIM PERFORMED UNCOMMANDED FULL NOSE UP TO FULL NOSE DOWN MOVEMENT. 'STAB CH 2 INOP' STATUS MESSAGE APPEARED. DISCONNECTED STAB TRIM. STAB TRIM RE-ENGAGED SEVERAL TIMES ON ITS OWN. INSTALLED SERVICEABLE HSTCU. OPS CHECKS OF STAB/YAW SYSTEM IAW 27-41-00.