Sims 4 Game merged 2 save files on its own.

I was playing sims last night and the game didn't crash or have any issues. I saved and closed like I normally do for this particular new save file I've been playing where I haven't done much to the world's around me and have only 1 active household. I open my game today and see a family from another save as the picture for the new save file. I opened the save file, and that families house to see the changes I made, plus the restaurants i added to different worlds were all added to my new save file as if I had merged 2 seperate saves. There is no way I accidentally saved that family and the restaurants to my new save because the new save is the only one that's been opened more a week now. Is there anything I can do to ensure this doesn't happen again? The damage isn't that bad but, if it was my file with tons if households and changes it could have done a lot if damage.

Thanks!!