Hello there is an issue where spawn lists are cleared and so your mod doesn't work when trying to add mob spawns, I think the mod might not be getting updated so I'm wondering if there is anything you could do to fix the issue pls

There is more information here: TeamGalacticraft/Galacticraft-Legacy#228

This is solved now see my last comment on this post for more information: TeamGalacticraft/Galacticraft-Legacy#228

Good job with your mod 5 years later since the last update on 1.12.2 and it still does everything ppl need.