@breckxo The problem is clearly something in your old Sims 4 folder, so you'll need to test out those files, at least the ones worth keeping. Start with mods and custom content, and if you have a lot of files to go through, use the 50/50 method:
https://modthesims.info/wiki.php?title=Game_Help:Finding_Problem_Custom_Content#The_50.25_Method
Once you've sorted through that content, you can move over the files inside the saves and Tray folders. It's best to move the files themselves, not the folders they're in. This content is probably fine, but test it anyway.
The rest of the files in the old Sims 4 folder are extraneous, other than Screenshots and Recorded Videos if you use those.
