I am having a similar issue. My Sims are also freezing in place during tasks; it was worse before yesterday's update. Sometimes, they would stay frozen for anywhere from 2 to 4 minutes (actual time, not the Sims clock, which continues to move; time doesn't stop). If I click build/buy, pause or go to manage worlds, they will usually unfreeze when I go back to the game.
It may have something to do with child Sims, as I didn't have an issue when the two children in the household were newborns (or before there were children in the household). It started when they aged up to infants (they are now toddlers). All the adults in the household vying to care for the children often caused an issue, as they can't all do the same task at once. But x-ing out the overlapping actions would sometimes set things back in motion (disabling caregiver autonomy has helped with that, too). I will mention that this happens every time I play, but to varying degrees. Sometimes it really affects gameplay to the point of frustration, sometimes it just happens a little bit and isn't a big deal.
I tried what puzzlezaddict suggested and played another household. I chose one with 5 Sims, one of whom is a toddler (my household has 8 Sims total, 6 adults, 2 toddlers). Everything seemed fine at first, no freezing. I went to visit the household I am having the issue with, and it was happening when I was there. I went back home, and the only time the game froze was when I was associating with the toddler. Not as bad as my regular household, but still, they would both stop moving for a few seconds or just nod at each other, not engaging in the current task.
I do have some cc in my game.