A320 FLT BROUGHT TO ABRUPT HALT AT GATE WHEN GND CREW WANDS WERE CROSSED ABRUPTLY. PIC TURNS OFF SEATBELT SIGN PREMATURELY WITH ACFT NOT FULLY PARKED AT GATE IN SFO; CA.

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PARKING ERROR DUE TO IMPROPER SIGNALS FROM GUIDE MAN. MARSHALER PARKED US AT GATE. WE WERE GIVEN A PREMATURE CROSSED WANDS SIGNAL FOR STOP TAXI AS WE APCHED THE STOP LINE. I STOPPED THE ACFT ABRUPTLY THINKING WE HAD OVERRUN THE STOP LINE. THINKING WE HAD COME TO THE END OF THE FLT; THE PARKING BRAKE WAS SET AND THE SEATBELT SIGN WAS RELEASED. THE GUIDEMAN THEN SHOWED US SEPARATED WANDS AGAIN AND STOPPED US VERY SHORTLY FORWARD OF THE POINT. WHEN QUERIED; THE EMPLOYEE ADVISED HE HAD NOT GIVEN US THE SALUTE. HE STATED THAT WE GOT ALL SQUIGGLY AT THE END WHEN I INTERVIEWED HIM. I APPLIED BRAKES ABRUPTLY BECAUSE OF HIS ABRUPT XING OF HIS WANDS; WHICH CAUSED THE ACFT TO BECOME 'SQUIGGLY;' TO USE HIS TERM. IT WAS NOT VERY GOOD GUIDANCE AND HIS SIGNALING WAS NOT CLR. FATIGUE AND AN ONGOING INFLT MEDICAL EMER INVOLVING 2 PAX WERE UNDERLYING FACTORS. NO INJURY TO PAX OR FLT ATTENDANTS DUE TO ABRUPT STOP AND SUBSEQUENT TAXI FORWARD. NO MISALIGNMENT OF JETBRIDGE WITH ACFT. FINAL POSITIONING OF ACFT WAS APPROPRIATE.