I now play university for the first time, and I've got exactly this bug too. Two Sims of mine moved into the dorm on a Saturday, and on Sunday (somewhere around 2 pm) the game froze, but the sound was still going on like voices from sims and trees were still moving in the wind. But I couldn't click anywhere, couldn't save or travel.
It is very annoying and disruptive, and I haven't figured out what causes it. I checked with my mods and without my mods, it was still there. Then I let the game create a new Sims 4 Folder, and it was still there with and without mods. Only when I started a completely new save and let Sims move into the dorm (with my mods) and fast forwarded like 4-5 days, and no game freezing. So I don't know if my precious 6year old save file is corrupted, but I am not willing to start over just for university. Otherwise the savefile works fine.
So my "workaround" is this:
1. Every few real life minutes I save, so if the game freezes again, I don't lose much progress. (Important: First I check, if the Sims are not accidently frozen in their looping animation. Only if they can move freely like walk somewhere, I save)
2. When the game freezes, I have to force my computer to close the game or completely shut down the computer, because sometimes I can't even access my desktop anymore. After that I open the game again, and load the latest save. But I don't let the Sim continue what they were doing before the game froze. Instead I cancel, what the Sim is currently doing and travel with him to another lot. So the game will not automatically freeze again.
I played one full week of university and my game froze like 5-6 times. But luckily I saved so often that nearly no progress was lost the entire week. Maybe this is helpful to someone else who has the same problem. 🙂
Some infos:
I play 2 Sims of mine, there are 8 nonplayed students as roommates. The University is Britechester.
When you look at the map of Britechester, there are two dorms on the map, one at the top and one at the bottom. I live in the bottom one.
I replaced the default dorm with my selfmade dorm, no CC used.