modpack: https://www.curseforge.com/minecraft/modpacks/project-architect-2

After removing all the light, I placed the rotten eggs and only spawn the mobs at first time, once they die they no longer spawn

Hello
Found this issue after looking for a 1.21 report on this. Project Architect 2 is mc 1.20.1 :)
I dunno if it's broken in 1.20.1, however I can confirm it is in 1.21 in ATM10.
Best regards,
Jin

Yes, this is happening in my world too the dreadful dirt is not spawning any mobs in the Direwolf20 1.21 pack

Maybe another mod is messing with random ticks? or a megatorch?
some more details like dimension and biome would be great as well.

I solved it by removing a forgotten megatorch.
Thanks to all!!

Megatorch didn't use to block those afaik?

Megatorch didn't use to block those afaik?

Ya even I remember it as not blocking the mobs spawning

megatorch hooks the spawn event, and cancels it.

Something must have changed somewhere though, either on mega torch mod side or this mod. You used to be able to have a mega torch in your base and also use the dreadful dirt. If that no longer works you need to setup your mob farm out of range of the torch, which is fine i guess, just less convenient.

Ah yes, looks like the old "NaturalSpawner.isSpawnPositionOk" was removed, and the suggested replacement is the event, which torchmaster is hooking...

Ok, ill attempt to stop megatorches from blocking this in 1.21, this shouldnt be the case in 1.20, because its not using the event, unless the megatorches are blocking it some other way i dont know of...