when i had a hopper that was full of gold nuggets (from a zombie pig man farm) some more were on top as it should have been because it was full and was transferring the items into the hopper however it was doing this for too long i tested it and that was the issue: hopper full of item (gold nuggets) while transferring to a empty hopper below, a few golden nuggets were left on top of the hopper and was causing the hopper to put them in but not get rid of them on top, so it was duplicating but not as it did before in 13w01b