You're just out of luck. Maybe try to reinstall it.
And yes, I’m the original author. Don't start spinning fake news or acting like a conspiracy theorist. Mozilla has full access to the source code, you don't need to inspect anything. If you don't trust Mozilla, then don't use Firefox.

For future readers: if you think the previous version works better for you, you can reinstall it from here: https://addons.mozilla.org/firefox/addon/enhancer-for-youtube/versions/

Don't forget to turn off automatic updates.