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.
Linked issues
Comments
Also - I can't consistently recreate this bug - it appears to be from the latest 13w02b snapshot... looks to be something to do with block updating / hopper orientation as re-placeing hoppers sometimes fixes the issue but if other hoppers/blocks are placed nearby then the issue comes back.
Duplicate of MC-6162.
This bug still exists in Snapshot 13w03a
I found an interesting quirk with this bug... if you have a the same setup on both sides of Chest A (so another hopper (say hopper C) pushing items into Chest A on its right, and another hopper under this (Hopper D)). (so it symmetrical pretty much)... I find that an item placed into Hopper A will be pushed to Chest A (incorrectly), but items placed in Hopper C don't get pushed into Chest A and are pulled by the hopper (D) underneath (correctly).