In previous versions of the mod, Thinking Forest and Wastelands had JUNGLE and PLAINS categories. This caused issues with other mods. I have updated the mod to change these biomes to have a categories of NONE, but this makes it so that existing worlds' biomes change in weird ways. This obviously breaks portal connectivity because portal connectivity is based on the biome that the portal is currently in.

Releasing a version of this mod where biome categories have changed but without trying to fix the biome issue will result in a lot of broken portals in existing worlds.

I am currently investigating ways to use Mojang's DataFixerUpper to change biome categories on load so they won't end up as broken, but we'll have to see how complicated this ends up getting.

This was actually caused by an old issue where adding a biome mod would reshuffle modded biomes. This has been fixed in recent versions of fabric api.