Ahhh that’s honestly looking like it’s tied into a landscape issue I’ve been tracking, that when the map has very high Z scaling everything that needs that data breaks down. What I’ve been tracking is how heightmaps like that can effect landscape brushes like the water system, but it seems you found another component of it.
Tough thing is I don’t actually have much of a workaround for this one, as past a certain size the crash is inevitable even if you don’t go over memory.