To reproduce:
- When you first start a game, send all villagers to a tree and chop till each at 10.
- Send all villagers to build mill
- Villagers can turn in wood at mill then switch to food
To reproduce:
This is not a bug. It is intentional.
If a villager builds any resource collection building then any resources it is holding will be collected.
It works the same way in AoE2.