EMB ERJ 135 ER/LR
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Confusion
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Flight Crew Overcame Equipment Problem
Aircraft
During descent on STAR; autopilot failed as aircraft leveled off at 11;000 ft. PF (Pilot Flying) took manual control of aircraft and held altitude of 11;000 ft. Aircraft momentarily dipped to 10;800 ft. after autopilot failed. We referenced the QRH; which did not offer a fix. Remainder of flight was flown manually without incident. However; after shutdown; trim ran to down position; without being commanded. Not sure if this was related to the autopilot failure.Not sure if abnormal trim was the cause of the autopilot failure.As all indications were normal prior the event; it is difficult to suggest prevention. While autopilots are generally reliable; automation still requires monitoring.
EMB-135LR First Officer reported the autopilot failed on descent; possibly related to a pitch trim issue.