raiders spawn on slabs and other non spawnable blocks breaking farms

ive noticed this bug about a 1 month ago in one of the snapshots when i went to use the farm and the raiders didnt spawn on the 5x5 ice platform above where they fall down to a kill chamber (image 1). the player gets bad omen falls thru the water elevator starts a raid kills the raiders and repeat but now this doesnt work for some odd reason. it seems to me the raiders attempt to spawn anywhere but on the packed ice blocks for whatever reason, ive seen them spawning on leaves, slabs, chests, and other blocks theyre not supposed to. please look into this as its very annoying, i dont want to have 2 farms broken in this world.