Time/Sim freezes while environment still moves

Lately I've been having problems with my played household members freezing.  I will be playing and they will all just stand in place with all their actions queued, however no one does anything.  Even the pets are just sitting there.  I have noticed this several times , however, i have not tried with different households to see if the problem exists.  I have not seen any pattern that would suggest a cause for this.  I don't use mods or cc.  The only fix I've found is to go out to manage worlds without saving (which is not always ideal).  Sometimes, that won't fix it, I have to exit the game entirely.  I've also reset the sims,  and I see the visual flicker that they've reset and their queue clears, but they don't move.  

It appears so randomly so I cannot say what the trigger is. I've even repaired the game to see if that helps.

To be clear, the household members freeze, but nothing else does...not the environment (for instance, steam cooker keeps cooking the meal, the tv continues to play, music continues, time continues, phones ring and neighborhood notifications continue).  Also, sims around the neighborhood/world, continue to pass by and even visit.  If I zoom out ( I am playing this household in Copperdale), I can see sims walking around the rides, stargazing, etc).