Its only i had a bad experience with UE4 Cook process (2 gb limit on landscape passed and critical error) and i removed even 2000 actors of my level to see what did i do bad.
I then noticed that i used visibility landscape mask as texture to landscape (to cut for making caves). When i removed the pin and made material opaque again it worked pretty nice again.
This was tested on 4.12.5 on 8 small landscapes in a persistent level. I have added 1.000.000 folliage instanced components and 10k actors latter but no problem at compiling…
The thing is, if someone gets stucked with this, i hope he can read this, i lost 5 hours trying to fix this problem, and in the other hand, if someone from unreal can explain why does that node destroy the level? (or advert it in official post, as it could have problems at compiling?)
everyone, and hope i can help someone. And it could be something i did bad, but i followed unreal tutorials to do it well and no errors, i checked it 10 times and see no missmatch.