So this is going to be a mass of text. I decided to install the add-ons that I have purchased in release date order, I know that I haven't purchased them in that order. I am making a list of the steps I took and their results. I also discovered that my game runs in DX9. Here is the info dump:
Base game downloaded and installed – no mouse issues
7/25 update downloaded and installed before testing fresh install
Started a new game and played for approx 5 minutes – no mouse issues
Downloaded and installed Get To Work – no mouse issues
Played game for approx 5 minutes – no mouse issues
Downloaded and installed Get Together – no mouse issues
Played game for approx 5 minutes – no mouse issues
Downloaded and installed City Living – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Cats and Dogs – no mouse issues
Played for approx 5 minutes – no mouse issues
** I then realised that the list I was reading from was just expansions, not stuff and game packs. I found a list that had everything on it, so...
Downloaded and installed Holiday Celebration, Outdoor Retreat, Luxury Party, Perfect Patio, Spa Day, Cool Kitchen, Spooky, Movie Hangout, Romantic Garden, Dine Out, Backyard, Vintage Glamour, Vampires, Bowling Night, Parenthood, Fitness, Laundry, My First Pet, Jungle Adventure, Seasons – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Get Famous – no mouse issues
Played for approx 5 minutes – no mouse issues
7/26 update downloaded and installed – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Strangerville – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Island Living – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Moschino – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Realm of Magic – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Discover University – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Tiny Living – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Eco Lifestyle – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Nifty Knitting – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Snowy Escape – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Paranormal – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Dream Home Decorator – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Cottage Living – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Blooming Rooms – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed My Wedding Stories – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Werewolves – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed High School Years – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Desert Luxe – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Growing Together – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed For Rent – no mouse issues
Played for approx 5 minutes – no mouse issues
Downloaded and installed Crystal Creations – no mouse issues
Played for approx 5 minutes – no mouse issues
Loaded previous game where the mouse bug first was noticed and played for approx 10 minutes – no mouse issues
I can possibly put it down to either doing a full uninstall and reinstall, or something in the patches that did something to fix it somehow? I don't know, but I did my testing, my mouse seems to be fine now. Unlike @emurphy07 I did not update my graphics drivers. I wanted to leave it until if the bug came back. We will see if it does /shrug
