Wandering traders that spawn in and despawn leave their llamas behind permanently and they never despawn. It gets rather annoying having your house filled with 8 trader llamas after being AFK for a while or have a bunch of trader llamas in your villager trading hall that you need to remove and you accidentally kill or let your villagers out by mistake. I've tried making the floor spawnproof with carpet and other spawnproof blocks but they wandering traders till spawn in and leave their llamas behind.