Background:
At the raid farm that I have built, my raids kept spawning on the ground. To combat this i placed leaves on the ground surrounding the outpost
The issue:
Placing these leaves seems to prevent the pillager outpost from spawning pillager captains and therefore giving me bad omen effect... however if I remove these leaves then the captains will start spawning again but the raid would spawn on the ground
This is how structure spawns work in Bedrock Edition: in order for the game to attempt a structure spawn (like pillagers in an outpost), it has to first make an attempt to spawn a mob somewhere else in the chunk on the same tick. So if the only valid spawn spot is the spot where the outpost spawns pillagers, then most likely nothing will spawn.
What you need to do is move your raid spawning platform and AFK location to > 54 blocks from the ground, so that nothing can successfully spawn down there.