This issue is happening in my world too. I had 10+ Llamas, sheep, and chickens in a fenced in area. It was not on a border chunk. I interacted with the llamas everyday and they also had been given name tags. The sheep and chickens were bred as well as fed. I had two turtles in an enclosed area, bred them, and they still despawned after 30 minutes or so. It is becoming frustrating because I could spend hours looking for a specific mob, just for it to despawn right after I interact with it.
This issue is happening in my world too. I had 10+ Llamas, sheep, and chickens in a fenced in area. It was not on a border chunk. I interacted with the llamas everyday and they also had been given name tags. The sheep and chickens were bred as well as fed. I had two turtles in an enclosed area, bred them, and they still despawned after 30 minutes or so. It is becoming frustrating because I could spend hours looking for a specific mob, just for it to despawn right after I interact with it.