What was found
(CAN) PILOTS REPORTED MACH TRIM & STAB TRIM MGS POSTED ON THE EICAS DURING CLIMB. FLIGHT CREW DECIDED TO RETURN TO BASE. UPON ACFT RETURN, MTCE INTERROGATED MDC & FOUND H STAB ACT/ACT JAM B1-007973 MSG LOGGED IN THE CURRENT FAULTS. CHECKED HSTA OIL LEVEL & FOUND IT ABOVE V GROOVE. HOWEVER, MTCE ALSO REPORTED EVIDENCE OF THE OIL LEAK FROM THE HSTA, TRACES OF OIL IN THE HSTA INSTALLATION AREA, & IT WAS DECIDED TO REPLACE ACTUATOR. HSTA WAS R & R, SYS TESTED OK. ACFT WAS DECLARED SERVICEABLE.