I'm having a similar problem, I'm not sure if it's exactly what you were experiencing, but my game also becomes unresponsive after playing for a while (anywhere between half an hour to five plus will cause my game to start reacting slowly/strangely on my laptop. Not sure if it happens on my desktop? Will have to test later.).
I can click things, but my sims ignore any commands, as if I didn't select anything.
For example, one of my vampire children died in the sun because he wouldn't take the command to move inside and simply stood in the road in front of his house until he burst into flames. :'(
I've also had a child taken away because my sims didn't take the command to feed them and stood there while time flew by. My sims will eventually stop taking care of themselves and die of hunger with full autonomy on.
I've had to reset games/not save after disasters like this, as I obviously don't want to accept tragedies by technical difficulties.
(Heck, I even wasted 10 IRL hours of my day teaching my sim husband to cook up Ambrosia to fix my OWN accidental sim death from "frozen in time syndrome" because from my save-point I'd die immediately from sun upon loading in. XD)
It's pretty frustrating to watch your sims die horrifically like that while they stand still and ignore your commands to save their life, I'll admit.
I have NO CC or mods. Just the base game with Vampires, City Living, Get to Work and Get Together expacs. Resetting individual sims via cheat does not help. Restarting game does help temporarily. If I remember correctly, this has been happening since before the last patch or two for me. I'm running Windows 10 with above recommended system specs and use Razer Cortex to help boost the game, nothing else I can think of that would affect this besides NVIDIA gfx settings, maybe. (which I've tried to change around, no noticeable effect?)
Also, the only thing that helps keep my sims alive is testingcheats on >mailbox>fill household/world needs>disable needs decay. At least with that, they won't die, but they will still stand there or continue the current action indefinitely unless I switch to another sim and speed up the time quickly from 1x to 2x and back. 3x time will fly by with no action from the sims, strangely. It's almost like all the sims are paused while game time passes.