I had some hoppers lined up pointing into each other from a chest (none were powered and I used a normal chest) and instead of the hoppers passing the item on it froze in the hopper and stopped there, it also would not move out of the chest.

To reproduce
Have a hopper going into a container block/other hopper and put a item in the first hopper
the item will not move
or~
place a hopper under a chest and put an item in the chest
the item will not move