Want to chime in here - in my experience, this is not a mod/cc issue. I removed all mods and cc, cleared cache, repaired, etc. and the problem remained for me.
Meanwhile, the Halloween holiday event had been scheduled for the following sim-day in the save file in question. The holiday had not actually started, but I had received the little pop up from the sim’s calendar that “Halloween is tomorrow”. So I recovered a save file from a few hours (my time) earlier, which took my game back a few sim-days. This save file loaded without errors.
Interestingly enough, this recovered save file that loaded fine was saved during the Prank Day holiday (2 sim-hours into the holiday itself). Perhaps the issue occurs when you save during the time between the little calendar notification of “[holiday] is tomorrow” and the start of the holiday itself?
Anyways, will try to get my game back to the point of the problem save, and will save again once it moves through the Halloween holiday. Then will try to load it and see how it goes. Will update then if I’ve found anything relevant.