Falling on land when over trees - how to prevent?

[Simbax]

Yeah, I was thinking it would be graviplants, but the description of the "bug" is too odd and ambigous to be sure. I can't believe a person could not know about graviplants, especially that this is the third mission on Tropica and there is no posssibility someone would not notice graviplants in the first missions.

EDIT: you got to be kidding me...