PAX DOUBLE SEAT UNIT REPEATEDLY BROKE LOOSE FROM MOUNTINGS AND ROCKED BACK.

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THE DEFERRED ITEM CALLED FOR REPLACEMENT OF SEAT ASSEMBLY 1A AND B; A DOUBLE SEAT SET. I ASSISTED 2 OTHER MECHS REPLACE THE SEAT SET. AFTER THE ACFT DEPARTED ON FLT THE SEAT SET CAME LOOSE IN ITS TRACKS. THE DEST OF ACFT WAS SBA. AFTER ARR IN SBA A FIXED BASE OPERATOR RE-INSTALLED SEAT SET 1A AND B. THE ACFT CONTINUED ON ITS NEXT LEG; WHICH WAS A RETURN TO SFO. UPON ARR AT SFO; THE SEAT WAS CHKED BY OUR MAINT MGR AND ANOTHER FOREMAN. WHEN THEY SAT AND PUSHED REARWARD; THE SEAT SET POPPED OUT OF ITS TRACKS AGAIN. THE 2 MGRS AND ANOTHER MECH AND MYSELF RE- INSTALLED THE SEAT SET AT LEAST 2 MORE TIMES UNTIL FINALLY; WE COULD NOT DISLODGE IT. OUR FOREMAN TOLD US THAT THE PROB OF THIS TYPE SEAT COMING LOOSE IS NOT UNCOMMON. MY FOREMAN AND A PERSON FROM ACR ENGINEERING HAVE GONE TO PORTLAND TODAY TO EXAMINE THE SEAT ASSEMBLY 1A AND B ON ACFT XX. A PAINTED BAND ON THE VERT LATCH WOULD PROVIDE A VISUAL INDICATION THAT THE LOCK IS FULLY DOWN IN THE SEAT TRACK HOLE AND ALSO INDICATE IF THE LATCH MOVED UP DURING TIGHTENING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR EXPLAINED THAT MANY ATTEMPTS WERE MADE TO SECURE THE SEAT AND; AFTER EACH ATTEMPT; THE SEAT TESTED SECURE. HE WONDERED ALOUD IF THE ACCESS HOLES IN THE SEAT TRACKS WERE NOT WORN BEYOND LIMITS. HE ALSO SAID THAT THIS PARTICULAR AIRPLANE WAS PURCHASED FROM A DEFUNCT AIRLINE IN A 'MERGER.'