Re: The Sims 4- game crashes when saving in my library and building in build mode.
@Bee3737 As a test, please try playing in a clean user folder. Move the entire Sims 4 folder out of Documents\Electronic Arts and onto your desktop, and when you launch the game, a clean folder will spawn with no content. Don't add anything to it yet; just start a new save and see whether you have the same issue. You can transfer your saves and other content to the new folder if you want, but leave that until after you've confirmed that the game is no longer crashing.
If you get a crash in the new Sims 4 folder, please let me know whether you use OneDrive, and if so, how full it is. Please also run a dxdiag and attach it to a post.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/