Reading books cause Sims to freeze?

Hello!

Whenever I send my Sims to a library, they eventually start to freeze after a while. They just stand or sit there, doing absolutely nothing as time passes. The game itself runs fine in the meantime, no lag or anything, it's just the Sims on the lot who don't seem to respond anymore. It takes ages until they start acting normal again. (Mostly a few seconds, which sounds much shorter than it actually feels.)

This happens wherever Sims can read, so I'm assuming this is caused by the books themselves? The freeze is barely noticeable at my Sims' home or at cafés, but nearly unbearable on library lots. There are also usually some (book) club gatherings, which doesn't help at all, since their members constantly start reading new books instead of finishing one.
The issue started to occur after a patch I think, but unfortunately I can't remember which one it was. It's been a while, though.

I use some CC, but removing it didn't help, so I don't think that's the cause.

My computer's a MacBook Pro (Retina, 15', Mid 2014, Version 10.10.5) and the game usually runs great on it.

Thanks in advance for any help! 🙂