When a chain of locked hoppers pointing into each other (see image) and the hoppers are briefly unpowered to let one item in each hopper to move to the next one, one of the items skips a slot and ends up in the second slot for some reason. It also only works with different items in each hopper. It does this with shulker boxes and I also tested it with different items in each hopper.

In the second picture you can see that the shulker box is in the second slot and should not be.

And if you cycle the items round again it skips that hopper entirely