AN A319 FMC DROPPED RWY APCH INFORMATION AND ATTEMPTED AN ILS TO A RWY PREVIOUSLY PROGRAMMED. AFTER REPROGRAMMING IT TRANSITIONED TO CAT II INDEPENDENT OPERATIONS THEN TRANSITIONED BACK TO CAT III NORMAL OPS.

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INBOUND TO ZZZ; FMC WAS LOADED AND BRIEFED FOR RWY XXL. DURING DSCNT; THE CREW NOTICED THAT ORIGINAL PERFORMANCE AND NAV INFO WAS DROPPED OUT OR SOMEHOW DELETED BY THE SYS. THE FO LOADED THE #2 FMC AGAIN WITH PROPER INFO FOR RWY XXL. ABOUT 5 MINS LATER; ADVISORY CAME UP DUE TO LNDG PERFORMANCE INFO NEEDS TO BE LOADED INTO FMC. THE CAPT UPLOADED THE FMC AGAIN WITH INFO FOR RWY XXL. APCH MODE WAS ACTIVATED; AND WE WERE GIVEN VECTORS FOR INTERCEPT RWY XXL. DURING INTERCEPT; THE CTLR CALLED WITH THE ADVISORY THAT THE ACFT WAS ON THE RWY XXR LOC; AND GAVE A VECTOR AWAY FROM APCH COURSE. IT SURPRISED BOTH CREW MEMBERS. WE ATTEMPTED TO CORRECT MANUALLY. THE CREW THEN SAW THAT THE FMC WAS AGAIN DISPLAYING PARTIAL INFO FOR RWY XXR. AGAIN THE FMC WAS RELOADED FOR RWY XXL. ACFT THEN DOWNGRADED ITSELF TO CAT II STATUS; AND 1 MIN OR SO LATER UPGRADED AGAIN TO CAT III. INDEPENDENT OP ADVISORY WAS DISPLAYED ON BOTH FMC'S MOMENTARILY AS WELL AS OPPOSITE FMC IN OP INFLT. THE SECOND APCH TO RWY XXL APPEARED TO BE NORMAL AND LNDG WAS ACCOMPLISHED FOLLOWING THIS APCH. IT APPEARS AS IF THE 2 FMC'S WERE OPERATING INDEPENDENTLY AND NOT XFERRING AND SHARING PROPER INFO. AFTER THE FLT; THE SUSPECTED IRREGULARITY WAS ENTERED IN THE ACFT MAINT LOGBOOK; AND AVIONICS TECHNICIANS WERE BRIEFED. THE FMC NEEDS TO GIVE VISUAL CUES WHEN IT IS CHANGING ANY INFO AUTOMATICALLY; AFTER IT WAS ENTERED MANUALLY BY THE CREW.