I believe I found a workaround for this error. I had an anti-enthusiasm hack in Sims UC and just hadn't moved it over, until I got a bunch of these errors. I got them while my Sim was in the pool building athletic skill (and the associated hobby enthusiasm). After putting this hack in, I had him swim until his skill was completely filled. I didn't get any more errors. IF I do get anymore errors, I'll come back and say that it didn't work after all, but for now it seems it did.
The hack I have is called Mel_removeenthusiasmglobal. I googled around trying to figure out where I got it from (I've had it for a decade) and couldn't find it specifically. But my search did turn up versions made by others, including some on Mod the Sims. So just search for global mods or hacks that remove/stop hobby enthusiasm.
