Bad Lag: Things to try:
It seems the Tray folder can be responsible for some of this. Try moving your tray folder to the desktop , then test to see if the issues remain.
Play off-line.
If it helps, then just put back into the new tray folder that has been generated in the sims 4 folder, the files of the sims and builds that you want or need to still have in your library. You can put the files back into the tray folder as you want to use the sims or builds in your game, then take them out again afterwards.
Of course this means spending some time sorting through all the houses and families that are important to you.
@MrsFlynn can you link your wonderful guides about zipping/saving the Tray Folder?
Zipping/Saving The Sims 4 Tray Folder1. Navigate to Sims 4\Tray folder:
C:\Users\<Username>\Documents\Electronic Arts\The Sims 4\Tray
2. Right-click on the Tray Folder -> Compressed (zipped) folder from the menu.
3. *Optional* Rename the resulting .zip file.
4. Move the resulting .zip file to a backup folder, flash drive or external hard drive.
Click on the posts linked below if you want to learn how to backup saved game files and organize the files in your Tray folder.
How-To: Save game files for Backup
http://www.carls-sims-4-guide.com/forum/index.php?topic=25262.msg428632#msg428632How-To: Organize the Files in the Tray Folder
http://www.carls-sims-4-guide.com/forum/index.php?topic=26535.msg442817#msg442817