The hopper priority system is not working, hoppers pulling out of a hopper from the underside do not get priority over the way the top hopper is pushing items.

Example:
Hopper A is a hopper on top pushing items into chest A on its left.
Hopper B is a hopper underneath Hopper A pulling items out of Hopper A and putting them into chest B below it.

When an item is put into Hopper A it goes straight into Chest A whereas it should go into Hopper B and into Chest B.