@Stardust547 When you installed Seasons, it sounds like you left your TS3 game folder (the one in Documents) in place. It, or rather any number of files within it, could have been corrupted by the install process.
The easiest way to troubleshoot now is to simply delet the five cache files in that game folder. They can fill up with old data and cause all kinds of issues, so they should be deleted regularly. Many of us do so after every play session. For reference, they are:
- CASPartCache.package
- compositorCache.package
- scriptCache.package
- simCompositorCache.package
- socialCache.package
If that alone doesn't help, pull the entire folder out of Documents and onto your desktop. When you launch the game again, a clean folder will spawn with no content. Try loading a new save in this folder, and then edit a couple of lots to see whether the objects behave as normal. If they do, copy the affected save into the clean folder and load it. If the save behaves normally, plus or minus some missing store or custom content, you can start transferring your other saves and everything else you want to keep into the new folder in batches. Be sure to test the game after each batch to make sure the issue doesn't reappear.
If your save is still behaving oddly in the clean folder, you can try saving the lot to the bin and replacing it. This should get rid of most if not all problems with the lot that remain.