Thought I would share some knowledge with you guys. I found a bug when editing a converted map from the original game. I noticed random patches of terrain that after a Rebuild had No plants or grass. and for that matter it didn't have that material's grass either. After I noticed it was not related to the grid square, I started digging deeper. There were some glitchy looking terrain that was around that whole area where there was no grass.
To fix this issue I thought back to the way things worked in the old editor. Height was a mud characteristic back then. To solve my problem I took the automatic brush and started erasing the area, and the area lifted way the glitchy spots, and had not patchy areas of plants in the area anymore.