Villagers Dissapearing from iron farm.

While afking next to my iron farm, using a farm showcased by docm77, All of my villagers seem to disappear. I have replenished them a couple of times and even named them to try and avoid any despawning. The entire iron farm is encased in a well-lit glass box. after many attempts, it seems that the villagers continue to despawn, and I am not quite sure why.

Thank you for your time and consideration.

 

sincerely John Lehew