Horses do not get saved when leaving chunks / Horses despawn

1. Place horses in pen

2. Fly backwards until the pen has unloaded from view & memory

3. Fly back, just like magic they will all have disappeared.

If you exit the game they will save when you relog the game. This also seems to happen with naturally spawning horses. Could not get an error report as it seems F3+C just closes the window down now with no actual report.