Attached below are some screenshots of a hopper sorting system I was working on for our servers chicken farm. The intended idea was that the feathers would be dispensed into a lava pool using a dropper, and the chicken would be left in the chest. This is not the behavior I'm getting. Instead, the hopper is "splitting" the items, and putting half of the feathers in the chest, while the other half is actually being sorted like it's supposed to. I've made searches on the site, and all mods are saying this is intended behavior, although according to the wiki and prior knowledge of this working before, hoppers should pull out items before they push items in. This means that I should NOT be seeing feathers in the chicken chest.

Also, here is a link to a video I've recorded demonstrating this point.
https://www.youtube.com/watch?v=L6a4QhNDloE

And if you would like to test this for yourself, a schematic has been created so you can import it using MCEdit.