Hi Umberto,
I've been spending some time lately at LAX in Prepar3D and have been encountering problems on the taxiways. While taxing on Alpha and Charlie I am encountering "boulder" like mounds poking though the ground which when hit cause the aircraft to crash. I think this also relates to a post just below mine regarding "taxiway A". I don't recall the intersection on Alpha, but it was at an overpass toward the west end. On taxiway Charlie, it is located between Charlie 6 (C6) and Charlie 5 (C5) and also over an overpass. The aircraft jumps, the engines shut down and the simulation ends due to a crash. I'm under the impression that the problems are related to the missing ground under the taxiways. I have my terrain mesh complexity settings to the maximum 1 meter resolution and all other sliders are full right.
Also on a seperate subject, after installing GSX, I have no approach lighting and no PAPI/VASI approach slope indicators at KLAX. The hold short lighting is functioning though.