I have remade a test, the only change is that's I have used Cathedral Assets Optimizer on Falskaar.
This time it doesn't crash even if I see some messages about out of memory during occlusion period when it loading the BTO files of the mod, here's the debug files.
https://ufile.io/f/a6kq9
Before my first message, I had try to generate occlusion by xLODGen, but it crash too. The new test that's I have just made is a success, so I'll remade my occlusion with xLODGen.