We are now looking at Epic for answers regarding this problem with RVT’s 
Hopefully this includes an online tutorial and documentation.
→ Waiting for Epic to fix these issues… Working on it, 0% complete…
It’s all fun and games on the forums to try and fix these issues but for us devs it’s the reason I have no hair left. 
I can only assume, nobody is using RVT’s and Virtual Heightfield Mesh commercially with a released product that works?