Many passive Mobs including: Villagers, Cows, Pigs, Sheep, Horses, Pandas, etc., despawn without reason despite being within a 12x12 space or less which is less than the expected despawn distance that is given. This mainly appears to happen whenever I leave the chunk the mob is active on for an extended period of time. There is no indication of wall suffocation since no drops are ever left behind and my villagers are kept in well lit areas with all of their necessities (beds, work station) and unable to leave those spaces and wander off. Every post I've read states that this should not happen to these types of mobs. Is this a bug or an intended feature and how do I prevent this from happening?