What happens is something interesting... I have a Redstone circuit, which does not allow the passage of other items, is the so called circuit "classifier or filter or coach items"; but my design is somewhat modified and whether what happens is that when introduced into the upper hopper a different filter item in the last hopper tour, appears duplicate items, that is, if they are gold nuggets that They are the filter and income, a whole stack stone becomes a whole stack of gold nuggets, not why this happens; in earlier versions to the 1.8.9 as 1.8.8, this does not happen, it is assumed that when another item than the filter is entered, it must be, in this case, in the chest but not this happens and passes this duplication of items.
Thank you for attending this bug, I hope you take into consideration for future updates and sorry if my English is a bit rough and not much and translated in Google translate.

PS: here I leave the map with the circuits in question!