Named Farming Villagers - Despawning/Disappearing Unexpectedly

When healing villagers for discounts and naming them, after unspecified amount of time they disappear when out of sight or left for a while with no possible way out. Zombie villagers name tagged appear unaffected as shown in screenshots. Latest disappearance took less than 48 hours for 12 farmers to go missing.

During testing the farmer villagers appear to be the only ones disappearing however in another area, librarian villagers remain and in greater numbers.