Time/Sim freezes while environment still moves

I keep hitting a bug where time will freeze but Sims and environment still move and I still have complete camera controls. I tried going to build mode in the meantime but then it deleted all windows and doors from the first level of the house. Sometimes I'll save it and it'll take about 2 minutes on average to save the game, but then it'll fix it once the save is complete. I had a Sim in labor when the bug hit which means I couldn't save it, couldn't enter build mode, or anything. So I had to force close and pray that I had remembered to save recently. I've already checked that it's not any of my mods or cc. It's making the game feel unplayable at this point until it's fixed.