My oldes and currently on used world called "XD" presents a problem in which hostile monsters do not spawn automatically at night or in caves. Monsters like zobies, squeletons, creepers or spiders don't appear. As same as vindicators and pilllagers don't spawn nor invade villages. Spawners do work, but the game isn't able to spawn them naturally as it should, even when it presents all the conditions for the mobs to appear.