Terrain paint disappears after leaving lot

Just started having this problem after the July update. Fresh blank save, no mods (because update), no CC. Was in build mode using terrain paint and if I clicked on the undo arrow, it would erase all my terrain paint (not just the last color used). Was also having terrain paint disappear when switching colors. Saved my changes, closed, and re-opened the game--all terrain paint was gone. After the re-open, saving changes to terrain paint did save. No screenshots unfortunately. 

I'm on PC and just had this happen to me.  I'm in a house in Brindleton Bay and, after travelling to an event in Windenburg, I came back to my house and all my terrain work has disappeared.  Please fix!

Me too, it's my first instance of this happening!  

Vanilla player. I hadn't had this issue anywhere until the recent update. I wonder if it's related to the paint feature being broken in regards to Sims as well?

+1 on this, and confirming some comments below. First noticed this after opening a new save today I only started yesterday, and seemingly "overnight" the terrain paint work was just gone from the lot I was working on. Then it also happened now whilst working on the lot again, right after switching to another type of terrain paint and clicking undo. (No CC used.)

Uploaded the save file here.

Quite sad to see that this is another case of a long-known error without a resolution. :(

Happened to me with my most recent build after the July update. I just spent weeks on this one only for it to be corrupted. Not sure why the original bug report was archived and this thread was marked as the solution if it's still an ongoing problem 7 years later. 

My terrain paint has been disappearing, even after I save the game multiple times sometimes it happens, sometimes it doesn’t, but it really kind of messes up my builds. I noticed another person posted about this bug, but it was over seven months ago and assumed it would be fixed by now. I don’t use any cc packs. 

Unfortunately this bug has been happening for years. And I mean at LEAST 6 years at this point. There is no workaround for it that I know of, I've just gotten into the habit of saving my lots to my Library periodically when I'm happy with how the terrain paint is looking. I REALLY wish they would fix this bug though! Its so common, and so frustrating.