I've been using hoppers in a contraption I'm building and have been noticing weird behaviour when pulling items from containers. I can confirm that this happens with chests and shulker boxes but it probably happens with other containers as well.

How to reproduce

• there is a world and a screenshot in the attachments but I will describe it as well.
• build a straight horizontal hopper line connecting two containers
• add a redstone line that disables all hoppers at the same time
• you can also add comparators for each hopper to see which contains an item
• put items into the container at the start of the hopper line

You will notice that gradually all comparators turn on, so it may seem like there is an item in every hopper. However this is not the case. As soon as you disable the hoppers using the redstone line you built you will notice that some comparators turn off.

Expected behaviour

Every hopper should always contain exactly one item. What seems to be happening is that the starting hopper sometimes doesn't pull an item from the starting chest.

In my opinion this is a dealbreaker for some contraptions like a few types of storage systems.