The site exporter now splits sidewalks and kerbs into ~20 m pieces (SEGMENTED / SEGMENT_M in Art/blender/site/export_site_fbx.py), 56 slices in all, so each has a bounding box that means something where it stands instead of reporting the highest point on a 279 m slope. They import and stage (63 site meshes in the demo map). The hypothesis behind it is dead, and that is the useful part: with the invisible sidewalk stopgap retired, the player now falls to Road_Hollywood at 366 - the slices do not block either. So the 279 m aspect ratio was never the cause; a 20 m slice of the same mesh fails identically. The sidewalk geometry itself is what does not collide, and the next place to look is its shape - an open surface with no volume, inverted winding or zero-thickness triangles - not the import flags and not the size. The stopgap retirement stands: the player walks on the road, which is real geometry that does collide, rather than on an invisible ledge.
850 KiBLFS
850 KiBLFS