A COMMUTER E120 DEVIATED L OF THE RWY 24R FINAL AND ENCROACHED ON A ACR B737 ON THE RWY 25L FINAL. PARALLEL MONITOR CTLR FOR RWY 24R WAS DISTRACTED BY CI-2 INTRAFAC COORD. RPTR FAILED TO NOTICE DEV. PM 1 NOTICED AND INFORMED TWR LCL CTLR FOR E120 TO CORRECT COURSE.

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I WAS WORKING THE PARALLEL MONITOR POS IN THE LOS ANGELES AREA MONITORING THE RWY 24R FINAL. CI-2 WAS COORDINATING WITH ME ABOUT THE POSSIBLE FAILURE OF RWY 24R LOC AND HOW THE APCHS BEING ISSUED WOULD CHANGE TO RWY 24L SIDESTEP RWY 24R. DURING THIS TIME I WAS DISTRACTED FROM THE COORD AND DID NOT NOTICE THAT AN E120 WAS DEVIATING L OF COURSE ON 2 MI FINAL IN DIRECT CONFLICT WITH B737 ON FINAL FOR RWY 25L. PM-1 NOTICED THIS AND CALLED TWR TO INSTRUCT E120 TO CORRECT COURSE. ILS FAILURES ARE COMMON IN THE LOS ANGELES AREA ESPECIALLY RWY 24R. THIS COULD HAVE BEEN AVOIDED IF THERE WAS A FUNCTIONAL BACK-UP SYS FOR THE ILS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THE RWY 24R LOC FAILED WHICH CAUSED THE E120 TO DRIFT L. RPTR WAS PM 2 AND HAD THE CAPABILITY OF OVERRIDING THE LCL CTLR FREQ FOR RWY 24 COMPLEX. RPTR SAID THAT THE PM 1 POS HAS THE SAME CAPABILITY FOR THE RWY 25 COMPLEX AND INDICATED THE PM-1 HAD TO USE THE VOICE LINE TO THE RWY 24 LCL CTLR TO HAVE THE E120 CORRECT BACK TO THE RWY 24R FINAL. RPTR DOES NOT KNOW IF THE 2 ACFT HAD EACH OTHER IN SIGHT. RPTR REITERATED THE STAFFING SHORTAGE BY ALLEGING THAT POS HAVE TO BE COMBINED IN ORDER TO RUN BREAKS. RPTR INDICATED THAT AT TIMES DURING BUSY TFC PERIODS; CTLRS WOULD NOT COMBINE POS AS COMBINING THE POS WOULD ADD WORKLOAD TO THE RECEIVING POS.