Hi there,

it might be the case that players have the mod AbandondedRuins_updated_fork installed which handles spawning ruins on surfaces, like planets. It might happen that players have suddenly ruins spawned on your surface which might not what you wish to happen.

If you don't want this, there is an easy fix available:

if remote.interfaces["AbandonedRuins"] then
    remote.call("AbandondedRuins", "exclude_surface", "<your-underground-surface-name>")
end

Replace <your-underground-surface-name> with your mod's surface name and no ruin will spawn underground anymore.

PS: I can see your mod supports multiple underground "surfaces".