Recently opened up a modpack I built many months ago and these mobs no longer spawn in any OTG world. Very weird as they spawned back when I first built the pack but now seem to be broken. What has changed to cause this and is there any chance for a fix?

OTG uses the Forge biome dictionary so it should be simple enough to use that as a spawn condition.

Can confirm same Issue on my side. OTG World with Biome Bundle, not a single mob is spawning.