Description of bug
Locked hoppers do not lock properly. They are supposed to stop items from flowing through them, but they allow items to flow through right now. Relogging, reopening the game does not solve it, and hoppers placed anywhere have the same issue.

How I discovered it
I was building an item filter when I noticed that locked hoppers do not lock like they are intended to. I tried relogging, reopening the game and replacing the hoppers or trying it in another spot does not solve the problem. I then tried placing three hoppers vertically pointing to each other to form a chain and locked the middle one with a block and a lever attached. I made sure only the middle one was locked (I had a texture pack on that showed whether or not a hopper was supposedly locked) and placed items into the top hopper. The items flowed all the way to the last hopper.

FYI, the item filter I build was 3:53 of this video: https://www.youtube.com/watch?v=BuL6rRHKnFc

How to recreate the bug
1. Place three hoppers pointing down and facing each other to form a vertical line
2. Place a solid block on the side of the middle hopper and place a lever on the side of the block (not the top or the bottom, the SIDE)
3. Place items into the hopper on top
4. Check the middle and bottom hopper. Due to the bug, the items would flow into the bottom hopper

Update: problem found, sorry for your time