Farmers not farming when full inventory of items

The bug

Farmer villagers stop farming when they have 8 stacks of items. E.g. when a farmer has 4 stacks of wheat and 4 stacks of seeds, or when 8 stacks of seed.

Also in survival, unable to give farmers 8 stacks of seeds, they only accept 4 stacks of seed. Need to use command to give 8 stacks of seeds to a farmer.