Hoppers when transferring items, randomize the order at which the items get moved along. Aka, the hoppers are not reliably in which items they will send when.

This has been a massive issue for every kind of sorting system for as long as bedrock has existed, and it makes things needlessly complicated!

You can see a demonstration on this bug in action here!
https://youtu.be/1ei2sEELbxY?t=169