Why does GPO no longer work?

[CrackersAndChips]

Some of you may have heard of the planet mod Gameslinx's Planet Overhaul by @Gameslinx. Personally, I never got to take a proper look at GPO's planets and moons, but it sounds pretty cool. Four new habitable worlds and a beautiful protostar? Count me in, that is if...    it were to work properly.

I have heard that GPO no longer works on the latest version of Kopernicus. I tried it out anyway on my copy of KSP 1.8.1, with Kopernicus and KittopiaTech 1.8.1-1 with Beyond Home installed. I modified Gaia's config to make sure that it wouldn't become the homeworld and I edited its moons' orbital properties to make sure that it orbits Gaia and not a renamed Kerbin with Gaia's properties. I also reparented Dread, Dres' GPO moon, around Olu'um on the opposite side of Telos' orbit. And it still didn't work. I then temporarily deleted my save and Beyond Home, and it failed to load when it was loading one of its Scatterer sunflares.

Now I want to know; why does this wonderful mod no longer work with KSP 1.8.1 and Kopernicus 1.8.1-1? Did something change with Kopernicus in the versions after GPO's last update? Did something required in GPO's supported Kopernicus versions get removed in the newer versions?

If anyone can tell me why Gameslinx's Planet Overhaul no longer works on KSP 1.8.1, please inform me. Any support is greatly appreciated.