I am currently trying to create an item sorting system. One of the main components of the system is having hoppers which go directly into a chest, and a hopper immediately right below it to capture any of the items which do not match what is in the chest.

I have experimented there's several different ways, a hopper that feeds directly into a Chest will no longer add any items to the chest and instead will go into the hopper directly below it.

This happens when there are no items in the chest or items of the same type in the chest.