Farmer villagers plant/harvest 4 or 5 crops then stop

Farmer Villagers will plant or harvest 3 or 4 crops then stop, and get stuck nodding their head as though looking for a new block then getting stuck.

Logging out then in will lead to them planting/harvesting 3 or 4 more crops, then stopping again.

This has been tested in survival and creative.

Initially I thought it might be because the farm blocks were over a minecart track, but this issues remains if the blocks below the farm grounds are solid.

I have attached the creative world showing the bug