try removing your mods folder first and putting it in any place (like your desktop). Then play your game without any mods and see if it still misbehaves. If it works fine, then the culprit is in your mods. This is what I'm also going through right now. I removed the mods folder and the game has no problem at all, I placed back some of the mods (including my creations) and all is still fine. Then I became too confident and placed back ALL my mods and my game is broken again. I'm getting really tired and exhausted (only had 4 hrs sleep trying to fix my game) removing and selecting which mods are interfering and not so I'm still playing with ALL my mods even if the persistent problem (of my disappearing sim) is really annoying me now. ...but maybe I'll have to pick on the mods again later when I'm not too tired anymore.
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