What was found
AT CRUISE AILERON FIRST OFFICER PFD INDICATION 40 LT OFF COURSE, LATER CHANGING TO 9R OFF COURSE. WHILE CAPT PFD SHOWED ON COURSE, FIRST OFFICER FLIGHT DIRECTOR COMMANDING A RT TURN CHANGING TO A LT TURN WITH AUTO PILOT 1 ENGAGED. CROSS CHECKED WITH A VOR SHOWED CAPT PFD CORRECT. AIRPLANE SYMBOL SHOWS ON COURSE ON BOTH SIDES. WHEN AUTO PILOT NR 2 WAS ENGAGED, IT STARTED RT TURN CORRESPONDING TO FIRST OFFICER LT DEVIATION ERROR. RE-ENGAGED AUTO PILOT 1, LATER RETURNED TO NORMAL. ACCOMPLISHED AFS TEST IAW AMM 22-96-00-710-001-A & BITE TEST OF VOR & MKR IAW AMM 34-55-00-740-002-A. NO FAULTS NOTED, COULD NOT DUPLICATE, ACFT OK FOR SERVICE.