I've only seen this happened on a farmer villager i know they work full day too unless it's raining(if only it's a farmer) not sure why this happens but if someone moves them or i do they continue to work if i don't do that they just stare at the crops, here's a video sorry for the quality i wanted to put it but it's too large so i compressed it.

Steps:
1. Sleep and Wake Up
2. Wait for the Villager to Work
3. Villager Works and Harvest Crops
4. Villager stops working and stares at the crops
5. If villager is distracted staring at the crop he will continue.

NOTICE
Resources Pack was Used.
Behavior Packs weren't.