What was found
(CAN) DURING CRUISE AN (AMBER) "STAB TRIM" & (AMBER) "MACH TRIM" CAS MESSAGES POSTED ON EICAS & AUTOPILOT KICKED OFF LINE. CREW WAS ABLE TO CLEAR CAS MESSAGE & RE-ENGAGE THE AUTOPILOT AFTER MESSING AROUND WITH THE STAB TRIM DISCONNECT SWITCHES ON THE PILOT`S & COPILOT`S YOKE . 20 MINUTES LATER THE (AMBER) "STAB TRIM" & (AMBER) "MACH TRIM" CAS MESSAGES POSTED ON EICAS & AUTOPILOT KICKED OFF LINE AGAIN.