Sims 4 Crashing in Build Mode

@Born4Randomness  Your dxdiag, and thanks for posting it, doesn't point to any specific problem with your system or the game.  Does the crash happen on all lots within this save, and in a new save?  Please test if you haven't already.  You don't necessarily need to abandon this build; it's just a helpful comparison.

If you're working with an existing Gallery build, or one of your own, please test it on a different lot and in a different save, and test the same functions on a lot on which you've never built or added anything.  It can be blank or a default EA-made lot, just nothing from the Gallery or your own library.

Your game should already be running in DX11 mode without any intervention, so you don't need the command line argument.

Okay, did some testing!
In the same save as the problem lot, the game does not crash when I edit stairs or terrain on a blank lot nor one with a house on it.
In a new save, it does not crash on a blank lot nor one with a house on it.
Went back to the original problem lot and tested it, and it does crash again.

@Born4Randomness  What lot are you working with?  And did you place your existing build on another lot, or just test with a different already-built house?  What I'm wondering is whether this issue is about this one lot in this save, this one build in this save, the combination of the two, the lot in general, or the build in general.

I am working with the 2 Olde Mill Lane (Henford-on-Bagley) lot.
I tested with already existing houses, not the one I built. Just now, in the same save and in a new one, I also tried placing my build from my library on the Twin Oracle Point (Newcrest) lot and testing it, and the game did not crash.
Seems like it's probably an issue with the lot itself, then? That sucks, I built this house specifically for this lot! ☹️

Okay, so I bulldozed the lot, built a couple random things, bulldozed it again, placed the original build back, and it no longer crashed when I edited large objects!

The game crashed in the process of me clicking exit game and I had to force quit, however. It did save my progress, though, luckily (whew, I was working on it for a while to test if it was going to go back to being fussy, so I'm fortunate that it didn't delete my progress).

So I think, at this time, the original problem has been fixed. If it continues to crash when I exit the game, I'll look into it further. But as the first problem has been resolved, I will mark this thread as solved.

Thank you so, so much for your help!! I'm super grateful, I was worried I'd lose my build!