B767-300 ETOPS OVERSEAS FLT SUFFERS AN EICAS FLAP SLAT WARNING AFTER DEP ZZZ2 WHERE THE SAME PROB HAD BEEN SUPPOSEDLY FIXED AFTER THAT DIVERSION. FLT CONTINUES WITH APPROVAL OF COMPANY WITH SAME INDICATIONS ON APCH TO DEST ARPT; MAKING A PARTIAL FLAP APCH AND LNDG AT ZZZZ; FO.

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THE ACFT HAD JUST COME TO ZZZ1 FROM ZZZ AFTER UNDERGOING HVY MAINT. WE WERE TO CONDUCT AN ETOPS VERIFICATION FLT TO CONFIRM THAT ALL OF THE MAJOR SYS WERE OPERATING NORMALLY AFTER AN HR IN FLT AND 20 MINS AT CRUISE. WE HAD DIVERTED TO ZZZ2 DUE TO A LEADING EDGE SLAT ASYMMETRY EICAS MESSAGE OUT OF ZZZ1. MAINT HAD TOLD US TAXIING IN AT ZZZ2 TO LEAVE THE FLAPS AT 20 DEGS TO HELP IN THEIR TROUBLESHOOTING. ON GATE ARR THE MAINT LEAD SAID THAT THEY WERE CHKING THE FLAPS AND SLATS; TRACKS; FAIRINGS; ETC; AND ASKED US WHETHER WE HAD CYCLED THE LEADING EDGE AND TRAILING EDGE ALTERNATE SWITCHES ON THE FORWARD PANEL; AS THESE SWITCHES 'RESET THE SYS.' WE TOLD HIM THAT WE HAD NOT DONE THIS; AS IT WASN'T ON THE LEADING EDGE SLAT ASYMMETRY CHKLIST. HE CYCLED THE 2 SWITCHES; AND THE EICAS MESSAGE AND THE LEADING EDGE LIGHTS WENT OUT. THE SYS WAS CHKED IN THE E&E COMPARTMENT; AND A BITE CHK WAS PERFORMED WITH NO NOTED DEFECTS. MAINT STARTED BOTH ENGS; PUT THE AIRPLANE ON SHIPS HYD PWR TO SIMULATE INFLT CONDITIONS AND RAN THE FLAPS ALL THE WAY DOWN TO 30 DEGS AND ALL THE WAY BACK UP TO ZERO; WITH NO EICAS MESSAGES OR ASYMMETRY NOTED. MAINT SAID THAT THE PROB WAS PROBABLY A COMPUTER GLITCH THAT WAS NOT CAUGHT IN ZZZ AND THAT THE SYS SHOULD NOW PERFORM NORMALLY. THE OVERWT LNDG INSPECTION WAS COMPLETED; AND WE WERE GIVEN NEW PAPERWORK AND DEPARTED FOR ZZZZ; FO. AFTER TKOF FROM ZZZ2; WE GOT THE LEADING EDGE SLAT ASYMMETRY EICAS MESSAGE AND THE LEADING EDGE LIGHT AGAIN. WE CLBED TO A SAFE ALT OBSERVING FLAP LIMIT SPDS. AT A SAFE ALT; THE CAPT ASKED THE OTHER FO AND I IF WE WERE COMFORTABLE WITH TRYING TO CYCLE THE LEADING EDGE AND TRAILING EDGE ALTERNATE SWITCHES ONE TIME TO SEE IF THE SYS WOULD RESET AND THE SLATS WOULD RETRACT; BASED ON OUR DISCUSSION WITH MAINT AND ON THE FACT THAT THE WAY THE AIRPLANE WAS FLYING; HE SUSPECTED WE HAD AN INDICATION PROB RATHER THAN A FLT CTL PROB. WE AGREED AND WE RECYCLED THE SWITCHES; THE EICAS MESSAGE AND LEADING EDGE LIGHT WENT OUT; AND THE SLATS RETRACTED NORMALLY. WE CONTINUED OUR CLB AND GOT ON A CONFERENCE CALL WITH DISPATCH; MAINT; AND OPS MGR AND ENGINEERING. WE TOLD THEM WHAT HAD TRANSPIRED; AND EXPRESSED OUR CONCERN AS TO WHETHER WE COULD CONTINUE AND VERIFY THAT THE AIRPLANE COULD GO ETOPS. THEY AGREED THAT WE COULD CONTINUE; AS THE SYS WAS NOW OPERATING NORMALLY. WE SENT THE PROPER CODE STATING THAT THE AIRPLANE SYS CHKED; AND PROCEEDED UNEVENTFULLY TO ZZZZ. UPON EXTENDING THE FLAPS FOR LNDG; WE GOT THE LEADING EDGE SLAT ASYMMETRY EICAS MESSAGE AGAIN. WE FOLLOWED THE CHKLIST; AND CONDUCTED A 20 DEG FLAP LNDG. AFTER BLOCK-IN; WE WERE MET BY A MECH. HE STATED THAT AFTER CLOSER REVIEW; IT WAS DETERMINED THAT WHILE THE AIRPLANE WAS IN ZZZ ONE OF THE SLATS WAS DAMAGED AND REPLACED AND THAT THE SENSOR WAS PROBABLY MISRIGGED. WE ALSO HAD A LARGE NUMBER OF CABIN WRITE-UPS ON THIS AIRPLANE AND IT IS MY OPINION THAT WE SHOULD NOT HAVE AN ACFT COME RIGHT OUT OF HVY MAINT WITH THE FIRST LEG BEING AN ETOPS FLT. WHENEVER POSSIBLE THERE SHOULD BE AT LEAST A COUPLE OF DOMESTIC LEGS TO IDENT ANY POSSIBLE PROBS.