Blending material functions

Since I’m not a power user of UE4 and based on my habits from v-ray and grasshopper I found a comfortable and “logical looking” way to mix landscape materials. Unfortunately, after adding more textures it keeps on crashing UE4. I spent hours figuring why but probably it’s better to ask.

It is a nested material function tree. Should it work? Is it a proper way to do it or I should avoid nesting like this? Maybe there is another problem? I’ve seen other landscape material techniques on videos for me they looked less clear.