As a village progresses and grows it seems to reach a point where suddenly the ability of the farmers to harvest and plant crops collapses on itself.

The problem starts off by seeing food on the ground everywhere and eventually farmers will harvest crops but not pick them up. Over time the farms get picked clean until there is nothing left. A check on the villager inventory in NBT Explorer shows that the villagers and farmers are winding up with full inventory slots despite those slots containing 0 items. It seems that once an inventory item is depleted the slot should be opened up again so the villager can once again gather new items. In fact I believe that the AI thinks the slots contain 64 items and this is why the villagers cannot pick anything up - it seems to be a dual problem: the villagers think they have full inventory so they pick nothing up, but, in reality the slots contain nothing so when a farmer gets hit with this bug he cannot plant anything.

This is especially bad for farmers because if their slots become corrupted they can no longer pick up the items needed to replant the farms (it seems to be mostly related to bread - once the bread is depleted the inventory slot stays occupied and if all 8 slots become like this the farmer can no longer plant crops).

I have made some screenshots to show the progression of the problem along with an image highlighting the issue as I found it in NBT Explorer - when I spawned a new farmer and gave him 128 seeds he was able to plant them without problem and once the seeds were planted the slots opened up as they should.

This does not happen when farmers are limited to crops such as carrots and/or potatoes - it happens when they get access to wheat. The assumption is that because harvesting of wheat results in drops of both wheat and seeds and because wheat is crafted into bread somehow this causes the inventory slots to get corrupted.

This was a fully functional and viable village and now it has collapsed on itself - the only apparent solution to this right now is to kill of all the villagers and start with new ones.