Terrain paint disappears after leaving lot

I have been experiencing this bug for years but just encountered a new twist. Because of the ongoing bug, I tend to save terrain paint for last which, due to my build style, means I tend to build out lots completely and come back later for final landscaping and terrain painting. Yesterday was landscape day for one particular lot in Willow Creek. I laid out the plants, a tree, two chairs and a table, and a debug car then I painted the terrain. Today I checked on that lot and low and behold only the initial paint I applied, scratchy in patches, stuck while the dirt and stone paint I laid out on top of scratchy in patches is gone. In the past when I have experienced this bug, all terrain paint from a session disappears but this is the first time I have had only "some" of the paint from a single session go "poof". 

PC, no mods nor CC