Turning off Crash detection solves the problem, so i suspect it to be another crashbox issue.
It's not a crashbox issue. No object in FSDT KLAX even have a crashbox to begin with, and thing you are crashing on it's the mesh, NOT the scenery.
As I've said in my previous reply, there's no invisible object anywhere in the scenery, and the crash doesn't happen in the scenery. It can only be caused by a combination of settings and/or 3rd party meshes. Those meshes aren't usually pre-processed and smoothed out as the default mesh is and, due to how FSX works, higher resolution mesh will *always* take precedence, regardless of the layer ordering in the Scenery Library.
Not all airplanes reacts in the same way to a terrain hump, so it's absolutely normal you might not see on all airplanes, but again, it's nothing related to the scenery.
A way we might prevent it in *theory*, would be supplying KLAX with a FLAT mesh of an higher resolution than any 3rd party mesh out there but this, on top of being a waste of memory (potentially causing OOM that users would attribute to KLAX, when if fact it would be needed to correct other 3rd party meshes faults), it doesn't really work in reality, because when using such higher resolutions, rounding issues and artifacts will creep in, causing terrain "spikes" that will cause crashes all the same.