Hi this is OP! i think i found a temporary workaround for this problem. I hope this comment reach ppl even tho it'll be way down there.
I just got a new PC (when i posted this report i was playing with a Macbook) so this is a completely fresh game, i haven't even transferred my saves, trays, etc so there are no mods or cache or anything that were suspected of being the problem. but my new sim still just started dancing with a townie despite playing on a fresh new save file on a new better device, i figured the problem is not the device or with/wo mods. so i tried removing 'heavy' packs, i moved Discover University and Eco Living folders to my desktop to try playing without them, and it worked for a minute, my sim could talk with several townies but they still cant sleep on a bed they just stood freezing.
then I tried to move almost all my packs into the the desktop and tried to play starting with ONLY 6 bigger expansion packs (city living, cats dogs, seasons, get famous, snowy, cottage), and they worked perfectly no problems at all! so i gradually added more and more packs, then played the game, added more packs, played the game, so on so forth to see how far my game could take before bugging again, when sims started dancing again i removed the pack (i did this without restarting my PC for every try/reset, idk maybe i should but i was too lazy and impatient). They finally worked with several expansion packs, game packs, and stuff/kit packs, I'll list the packs that worked for me below.
after the game was stable-ish i started transferring my older saves, i literally just replaced the whole new Electronic Arts folders w my old one i didn't remove the old tray folders or cache or thumbnail.cache things or whtv and the game worked alright. i even added the (newer updated) mods that I used to have and they still worked well, only bc i wanted to prove if the mods are the problem but it were not. I've been playing for 2 hours and so far so good.
So i think the problem with this bug is probably if you have too many packs (??) i'm not sure. Removing the bigger packs like Eco Living, Get Together, For Rent etc i found helped a lot but i'm not sure if they're the main thing causing this problem? I don't think removing the smaller kits would do much unless you have like over 30 kits, and i found removing big game packs like vampires and wedding stories that had their own worlds could be significant as well. I could try removing Lovestruck (as it was probably the start of Bugs Era) and it would probably help but i refuse to play without it bc it's so fun and made me laugh a lot so i had to compensate and remove other packs that i don't play with that often.
But this shouldn't have to happen?? We shouldn't have to do this, i mean we should be able to play with any packs that we have and even now that i have a new waay better device i unfortunately still couldn't play with everything. So there's that I hope this helps, you can try mix matching your own packs and see how far your game could take. Good luck!!
Packs that I haven't removed:
EP: Get to Work, City Living, Cats Dogs, Seasons, Get Famous, Snowy escape, Cottage, HS Years (the next one i'll remove if i have to), Growing tgt, Lovestruck, Life Death, Business, Enchanted by nature
GP: Dine Out, Parenthood; Kits: Incheon, Blooming rooms, Desert Luxe, Pastel pop, Everyday Clutter, Book nook, Home Chef, Goth, Paranormal, Comfy Gamer etc (the kits aren't that heavy so having many kits is still ok i think. Bc having that much EPs with many GPs but few kits still won't work, so i compensated lots of GP so that i can have that amount of EP and many kits)