Whenever you have double objects on an airport, the culprit is never the airport itself, but another scenery in conflict, which in this case is likely the OrbX, which comes with an AFCAD for KLAX, which must be removed if you are using an add-on for KLAX, like the FSDT KLAX.
Sometimes, such conflicts can be solved by installing the airport last, so it will stay on an higher layer on the Scenery Library but, if this doesn't fix it, you must remove the offending AFCAD manually, when the sim is not running.