Freelance career bug - writer can't finish books & writing skill broken

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? Every time (100%)
What is your current game version number? 1.51.77.1020
What expansions, game packs, and stuff packs do you have installed? All
Steps: How can we find the bug ourselves? Join the writer branch of the freelance career and try to write a book for the client
What happens when the bug occurs? Can't finish writing a book for the freelance writing career gig, writing skill won't increase whilst writing the book.
What do you expect to see? The sim can write a book, his writing skill increases as he does, and he can complete the book and give it to the client to complete the job.
Have you installed any customization with the game, e.g. Custom Content or Mods? Yes
Did this issue appear after a specific patch or change you made to your system? Yes
Please describe the patch or change you made. v1.15

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When my sim tries to write a book for the writing branch of the freelance career, his writing skill doesn't increase and the progress circle around the action doesn't move. I have to cancel the action and resume writing to see the progress, but when the book is supposed to be finished, it doesn't show in my inventory and is still available to "resume writing". When I click that action it just cancels immediately. The writing skill does increase when I practice writing, but not when writing actual books for the career.