The key thing you said is that it doesn't happen when you have your mods turned off. I have never seen that notice you show in the pic before, so it almost has to come from a mod that you have. Just because it worked fine before the patch and now causes that notice to keep popping up is a clear indication that there was something new in the patch that is triggering it and the mod needs to be updated. So you need to figure out which mod it is and either update it or remove it. Based on what the notice said, I would first look at any mods that affect death or life spans as I get the impression that whatever mod it is, it has made your sim immortal and unable to die.
And I would suggest you take a look at all your mods and update any you find have been updated as well.
Hope this helps.
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