Sims keep freezing

Not sure if this is exactly the same issue, but similar enough and I can't find another report like it. 

After the update this week, I played on Thursday in my vanilla save to do a quick toddler birthday before adding mods back to my game and switching to some of my modded legacy saves. I'm consistent about repairs, clearing cache, etc on my game, but when I loaded into my save on Thursday there was extreme lag. I still went ahead and ran the birthday party. I invited a handful of sims to it. Between the household (7 sims 1 being a pet) and the guests (7-8 cant remember) I had 14-15 sims on the lot at once with 6 being playable. During the party, I attempted to have one of my household speak to another sim (pictured below). 

However, it turned out that guest was frozen and the household sim also ended up freezing. I could NOT reset either sim. They were frozen exactly like this as though they were statues the entire time. Another guest also got caught in this blackhole space where my sims were frozen, but she was able to be reset... sort of. She rest and reappeared outside but was frozen where she was. At the end of the botched birthday, the frozen sims could not leave the property--the two adult sims and one child--and my playable sim was still stuck. I had to travel to the frozen sims' lot where they were once again home to get everything back to normal.

Once I exited, I repaired my game and cleared my cache and then reopened my game. The lag was gone, but I didn't try another event until last night when playing a legacy challenge and hosting a MWS wedding. This was a modded save, but the issue I had with the sims freezing and not being able to be reset was the same as in my unmodded save though in this case it spread to far more sims and started with my played sims. For this event, I do not remember the exact number of sims on the lot, but the household was only 2 sims, then adding the fiance, a sim of honor, flower pal, and officiant (the ring bearer was a part of the household), and maybe about 10 or so guests, I'd say there were about 17 sims on the lot at the time. 

Unlike in my unmodded save where the sims didn't even start T-posing, some sims did start to but it was not consistent and my sims and their guests were once again stuck until I went off the lot and came back. 

Some sims, like in the unmodded save, were moving around just fine. My played sim was still queuing up actions including "eat the cake" from the cowplant which she "successfully" did even though she never moved. 

Again, while this is my modded save, the issue is the exact same as in the unmodded save so I wanted to share for additional information. I don't know if this would be a fully separate issue from the one OP is describing or not, but I've never had this issue before in my game.

Based on what I've experienced between my Thursday and Saturday gaming sessions, the issue seems to surround events (and possibly events with a larger number of guests), because I did run a Bach Party the day before the wedding with only the bride and about 4-5 other sims and there were no issues then. I realize MWS has issues, though I know there's been many fixes to it, but I really don't think this is mod related or MWS specific since the birthday party was the first instance of this issue. I've run a successful base game wedding (back in June before I had MWS) with a large number of guests, so this is a new bug for me.