Hoppers were backing up for unknown reasons.

Steps to reproduce (shown in

)

1. Load the world linked below.

2. /tp 128 66 7 facing 128 66 6

3. Notice the bonemeal item frame in front of you attached to the barrel, which is fed by a hopper behind it under the red carpet. That hopper is fed by another hopper, which has two more hoppers above it. This is a slice of an item-filtering storage system. The hoppers pointed horizontally toward the right at Y 68 are know as a "hopper pipe". The hoppers immediately below the hopper pipe are set up as a "filter hoppers" with a filter item in the first slot and dummy items in the remaining slots. These pull items that match the item in their first slot down from the hopper pipe. Where you stand at X 128 the filter hopper is set up to pull bonemeal.

4. In order to observe results more easily, break the smooth stone block under the item frame with bonemeal in it, then break the hopper below the barrel. This allows bonemeal to collect in the barrel instead of being pulled down into the barrels below.

5. Get 4 stacks of bonemeal.
   These tests show how the filtering works:

6. Place a single bonemeal item in the hopper at 128 68 2, then check the barrel with the bonemeal item frame on it at 128 66 4. The bonemeal should have been automatically transferred to the barrel.

7. Place a single bonemeal in the hopper at 117 68 2, then check the bonemeal barrel at 128 66 4.

8. Place a small stack of bonemeal (8 items or so) in the hopper at 117 68 2, then check the bonemeal barrel at 128 66 4. All of these bonemeals should have been automatically transferred to the barrel.
   These steps reproduce the bug:

9. Collect all of the bonemeal from the barrel.

10. Place your 4 stacks of bonemeal into slots 2-5 of the hopper at 117 68 2, leaving the first slot empty. Leave the hopper UI open to watch.

11. Wait until you see a poppy come into the first slot of the hopper followed immediately by an iron ingot (iron golem loot from a farm nearby). If more than a full stack of bonemeal has drained by this time, then retrieve the bonemeal from the barrel 128 66 4 and place it back into the hopper at 117 68 2.

12. Wait a few seconds, and then check the bonemeal barrel at 128 66 4.

Expected result

All of the bonemeal gets filtered to the bonemeal barrel.

Observed result

The bonemeal no longer gets filtered to the bonemeal barrel.

These steps illustrate how the bug is happening:

1. Immediately after step (12) above, check the hopper pipe just before the bonemeal slice (127 68 2). It should have a bonemeal in the first slot, showing that bonemeal is being transferred through the pipe. Be careful not to accidently pick up this bonemeal due to MCPE-164754, or you will stop the bug and not be able to follow the steps below.

2. Check the hopper pipe just after the bonemeal slice (129 68 2). If the bug is happening, it will have bonemeal in the first slot, showing that bonemeal is being transferred through instead of being filtered at the bonemeal slice.

3. Check the hopper pipe at the bonemeal slice (128 68 2). If the bug is happening, there will be an iron ingot or poppy in its second slot. You may or may not see bonemeal flickering in the first slot.

4. Check the filter hopper in the bonemeal slice. If the bug is happening, its bonemeal level will be a constant 41.

Expected result

All of the bonemeal gets filtered to the bonemeal barrel because the filter hopper with bonemeal pulls it down from the hopper pipe.

Observed result

The bonemeal is not pulled down by the filter hopper because the pipe hopper at 128 68 2 pushes it out in the same tick in which it is pushed in by the pipe hopper at 127 68 2. MCPE-166990 details how this instant transfer past filters happens in general with predictable probabilites. The distinct issue in the present report is it happens 100% of the time on a chunk border in the specific build in the test world.

I was moving items into one of my storage warehouses like normal. Items were moving from my mob farm, and iron farm as normal. Then I crafted a large amount (double chest) of bone meal and sent that into the warehouse. For some reason the warehouse sorting systems then began to backup. If you review the video I attached, the system was stuck with one piece of coal in the second slot of a hopper. As soon as that was removed sorting returned to normal. Then a few minutes later a iron ingot got stuck in the same hopper in the same slot. Once I removed that items began to sort like normal. I didn't experience this issue on 1.19.50 and this isn't something that I haven't done before. I have attached a video so you can see the issue. 

https://drive.google.com/file/d/1VeuNSB5LIcaWLd6QQPUKtm4qzfU_-DGq/view?usp=share_link

Here is a link to the world download,

https://drive.google.com/file/d/1DZby8cQ5LU9ykvaUt5Mgb-A5wbyuP0R7/view?usp=sharing

Steps To Reproduce

1. After loading into the world go to coordinates 176-47-20. There will be a command block in front of you with a button. Press the button and the game will be switched to difficulty hard.

2. Go to coordinates 161-47-2. Behind you there will be a leaver. Flip this on and a trident killer will be active. Let this run for about 5 minutes. The items from this trident killer, and my iron farm will be flowing into the warehouse.

3. Go to coordinates 141-47-1 and fill the input double chest with bone meal. This will automatically start to unload bone meal into the warehouse above you. To get the error to occur you should let this chest empty about half way.

4. Go to coordinates 128-66-5 and look at the upper most hopper. When the error occurs there will be an item in the second slot of this hopper. The most common item I've seen get suck in here is coal or an iron ingot. If you remove the item stuck here then items will start to flow normally.

It appears that when an item gets stuck in this hopper. Then the items that should be flowing into the first slot of the hopper are going right past the hopper and into the next one in line. Again as soon as the item is removed from the second slot of the hopper items begin to flow normally again.

Also, I did notice that at times you may have to fill the chest at 141-47-1 multiple times, but most of the time in my testing I only had to fill this once.

Observed Results:

An item gets stuck in the second slot of a hopper, and items that should be flowing into the first slot of the hopper are bypassing that hopper completely. Once offending item is removed from second slot of hopper, items flow normally again.

Expected Results:

No items should get stuck in the second slot of hopper. Items should flow normally.