If you create a hopper sorter in this well known configuration,
http://i.imgur.com/XR2maT3.png
With 18 of an item (like bones) in the first slot of the top hopper and the remaining slots with 1 of the same item,
And if you have a row of hoppers above this feeding to many of these sorters,
Only half of the items will pass into the sorter. The rest of them will continue along the row, usually meaning they are lost.
The expected behaviour is that an item should always be sucked into the hopper below (if there is space for it) before it is pushed to the adjacent hopper (that is indicated by the direction its "spout" is pointing).
Comments 3
I'm unable to reproduce this bug. Despite having tested every orientation (just in case) and in 14w06b as well.
I'd also like to add that the expected behaviour for the hopper below is to pull an item from the hopper above every 4 redstone tick, not always.
My guess is that you actually put a whole stack directly in the hopper above your filter. In consequences, the filter pull an item from that hopper every 0.4 second, and the said hopper push an item in the next hopper of the chain every 0.4 second too. Halving the number of items actually pulled by the filter. If this is what you did, then it's a perfectly normal behaviour. You can't put a whole stack directly in the hopper above your filter. You have to feed that hopper only one item at a time too.
If this is what you did: Work as Intended.
If not: Cannot reproduce, please provide a world save or a better explanation.
Work as Intended
Sorry Hartspoon, you are right. I'd incorrectly tested it by putting an item in a hopper directly above the two hoppers in the image, rather than them feeding one at a time.
I originally thought the sorter wasn't working because the mob farm rates had become greatly reduced owing to the mob spawning bug.
It's seems unlikely since you're feeding the system with hoppers, but are you sure you're not providing items to that "filter" hopper faster than 2.5 items per seconds?
Could you provide a world save with that system? I made many sorter and they all worked well without skipping items like that. I'd like to see it happen to understand where is the problem.