[BUG](Editor) Grouping and Erase functions not displaying correctly

[mantha16]

On the left is how some terrain looked after id used erase and grouping.  on the right is how it looks after the level was saved, closed and re-opened.  Additionally some groupings move out of position and cant be easily moved back due to the erased terrain showing up again.

I would add that if you launch NL and go to the level it displays correctly but if you choose play level from the editor it does not.

Also I dont know if its related but i cant copy from one level to another i get an error message that wont go away and have to use task manager to close the level.