Issue with Mod with biomes - Errors in currently selected data packs prevented the world from loading

Hello! 

So I have a mod. It contains 2 biomes that I've set up in MCreator. It plays just fine, but if I then remove that mod from Forge and try to load any world that previously used it I get the message - 

'Errors in currently selected data packs prevented the world from loading'

It gives me the option to load with only the Vanilla data pack, but then I just get -

'invalid or corrupted save data'

If I remove the biomes from the Mod and go through the process again I don't have this problem. What is it about the biomes that is causing this and is there any fix?