Hi, thanks for the files.
There is something unusual in your scene: "ForestIvy001" is using "ForestIvy002" as surface object. That may generate unexpected results.
Please, can you fix it and check if that solves the problem ?
You can see the assigned surfaces from Maxscript, using "$.surfobjects", as shown in the attached image.
The wrong assignment can be fixed using "$ForestIvy001.surfobjects[3] = undefined".