I think the problem is that this script uses some code from other userscripts (Keisei/Niai), and that other code recently broke after some changes in WK. Today, I have attempted to fix the Keisei/Niai scripts. By changing the Rendaku Information script to use my fix, it should hopefully also work again. I have sent a pull request to @nonymouse, so you can wait for them to maybe merge my fix. Alternatively, you can immediately update here: