Terrain paint disappears after leaving lot

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I have this, too. It happens when I use CC paint, but not in Henford-on-Bagley. That's all I know, so far.

This is happening to me without leaving the lot or reloading the game. It seems to be getting triggered by switching to a second type of terrain paint, then pressing undo. If I undo with multiple types of terrain paint on the lot, it will just delete all of the terrain paint rather than undoing my last stroke.