kylef06 All I would recommend is making periodic backups of your user files, either the entire Sims 4 folder or at least the saves and Tray subfolders. I dump my extra saves on an external drive, probably not as often as I should, but you can also use cloud storage if it's easier; Google Drive is one option that offers some free storage, and you have access if you have a gmail account.
You could make a local backup too, as in, on your computer. It's not as reliable since it could be erased by general computer trouble, but it's better than having nothing at all.
Build mode does seem to be running worse these days, at least for some users and in some contexts. I don't have any suggestions for that, unfortunately, other than to hope it gets fixed in a patch sometime soon. It should at least be on EA's radar.