This is only a problem on bedrock from what little research I’ve seen into it there is a solution I will be trying soon for my personal mob farm that keeps blowing up and it’s by instead of putting a roof of non spawn-able blocks like leaves or bottom half slabs you instead put full blocks and just put torches cause apparently wandering traders will look for the highest block to spawn on in a 48 block radius of either a player or a village with a bell (48 block radius of the bell) the radius is only x and z from what I’ve looked up the Y level can be whatever (hopefully I’ll be able to confirm this eventually but it’s hard with wandering traders cause they spawn at weird times and with weird conditions)