Entities are going through blocks

I'm trying to build an iron farm in a void map. When I try to spawn a villager with an egg but he goes through the block into the void. Same problem with summon command. I tried with other mobs, they have the same problem. I noticed that the problem happen only with blocks higher than Y= 16. Above Y= 16 the blocks are looking missing, but the villagers and mobs are taking damage going through solid blocks.