Mobs Spawning In Stair Blocks also and well lit area

hostile mobs like creepers zombies etc spawns on the roof of my houses w/c are made of oak stairs, im pretty sure this should not be possible specially it does not happen on the java edition.
also theres this bug where mobs still spawn on well lit area theres this one place in my shop where thres only a 3 block space with torches on botsides and a glowstone above but still keeps spawning mobs