Solved
Sim can't write books
When trying to write a book, sim keeps canceling the action within a few in-game minutes of attempting the action.
The bug thankfully hasn't happened in a while. I suspect it was caused by a bug regarding a "judge decor" action constantly trying to interrupt the current action, as whenever the Sim finally could complete that action (it would also auto-cancel most times), he could finally return to writing a book without that action being interrupted for at least a few hours.
And to answer the questions, no I don't use mods or CC, and I play on PC.
