As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, WHEN A/P "A" IS ENGAGED THE AIRCRAFT STARTED UNCOMMANDED LEFT ROLL. DISENGAGED "A" A/P. "B" A/P WOULD NOT ENGAGE. CYCLED YOKE SWITCH NIETHER "A" OR "B" A/P WOULD ENGAGE. FINALLY GOT "B" TO ENGAGE BUT IT WOULD NOT FOLLOW ANY MODE CONTROL PANEL COMMANDS. ITEM IS OPEN AS TO THE AIRCRAFT IS ON THE GROUND IN WORK.