Flat Diagonal Roof Glitch

Product: The Sims 4
Platform: PC
Which language are you playing the game in? English
How often does the bug occur? 100% (Both of the times I've tried it so far.)
What is your current game version number? 1.111.102.1030
What expansions, game packs, and stuff packs do you have installed? All except for a few kits.
Steps: How can we find the bug ourselves? Place a diagonal room on the ground floor, a square room on the second level, and a square or diagonal roof on the third level. Place a hipped roof on the top room and flatten it. Do the same for the second level, then the ground level.
What happens when the bug occurs? The first two roofs behave properly, but the third (lowest level) roof won't flatten and then it cannot be removed, the undo button won't do anything, and the game fails to save (in build mode or live mode - I've tried both ways.)
What do you expect to see? I would expect the roof to flatten, or to be removable. If not, the undo button should remove it. The game should save either way.
Have you installed any customization with the game, e.g. Custom Content or Mods? I removed them.
Did this issue appear after a specific patch or change you made to your system? Not sure.

As described above, I was trying to make a building that basically looked like a stack of presents when I found that the lowest roof was causing a glitch of some sort. I removed the only three mods I had in at the time, cleared the cache, and tried again but the same thing happened. I realize this is a relatively unlikely scenario, but it seems to be a problem nonetheless.

I just tried a third time (still without any mods), saving every step of the way to see how far I could get. This time, I added the final roof and removed it before attempting to flatten it. But then it wouldn't let me place a new one, and I couldn't delete the roof on the second level either. And then the game closed itself entirely.