Can someone help with this, I'm trying to Demonsterize as a unified Centaur Caehn and after subjugating, invading and pillaging to my hearts content I'm trying to Demonsterize and like the eloquently named Lord Sir FunkyFresh here, I've taken maybe 8 or 9 events over the course of a dozen years or so to lower monstrous stat and am still at "Very Monstrous". Is this a bug or is there an event or something I'm missing?

You'll probably need to do more than 9 events. Like, it took me 23 years in my test run (23 years to be semi-monstrous, tier 2, that is), 50 to be fully welcomed. Also, keep in mind, certain things will just utterly prevent you from de-monsterizing like having a bad ruler with a "monstrous" traits.

However, I do want to just say that, mechanically, you shouldn't de-monsterize ever (it's just too many monarch points down the drain. Also, the only real benefit is for you to seem more popular to the very people who refused to see the inner beauty that was inside you all along. Never change! It's those bipedal monkeys who are wrong!). Anyways, if you're roleplaying then de-monsterizing is a fantastic idea and you should definitely do it because it opens up politics/sets the world stage in a very lovely way.

Edit: oh, I also did the test run with the redscales culture and didn’t run into any problems relating to monsters so that might’ve been fixed?

The "mean time" for demonsterization to happen is expected to be around 100 years. Obviously you can do it much faster, but not having your status change after a decade is normal