There is an inconsistency when it comes to item collection systems seen below. It would be great if this bug could be fixed since it has been around for such a long time. Every storage system I use is huge and clunky due to this bug. It just would be easier if the inconsistencies I am about to describe are fixed.
The problem here is that these item collection systems require the use of directional placement, which means that it only works correctly facing a certain direction. The ONLY direction that works 100% correctly is the North. As you can see by the image below, the North has grindstones as the block to put an item between the ice and the blocks. Here, the items slide perfectly fine on the ice. The redstone block next to the hopper means that the North side will collect items correctly using this method of item collection.
From there, things get weird. The East and South side function the same way in that they have to use chests in order to allow the items to slide on the ice while also being able to be collected by hoppers. So the limit here is that you have to use chests and you cannot use grindstones, honey blocks, anvils, and other <14 pixel wide blocks.
The biggest problem and inconsistency occurs on the West side. On the west side, you can use any <16 pixel wide block to have the items slide on the ice while also allowing hoppers to pick the item up. However, as you can see, there is no redstone block next to this hopper. This is because for some strange reason that makes zero sense to everyone, this hopper will not pick up the items like the 3 other cardinal directions do. This inconsistency is the reason I am creating this bug report in the first place.
So, feel free to try out this bug in Bedrock Edition. Build what I have below or something like it and play around with it. I'm very sure that professional mincecrafters who build giant farms and huge projects have probably experienced this bug once. This is a bug that should not exist, so please give this bug report some attention so we can help to make Minecraft a better game one bug at a time!
[media]Steps to Reproduce:
Build a row of packed ice with a row of normal blocks directly next to each other.
Put a chest at the beginning of the row of normal blocks.
Place a hopper somewhere among the normal blocks.
Make a water stream running one way down the ice.
Throw an item so that it hits the chest and slides down the ice path.
Repeat steps 1-5 in all cardinal directions (rotate the build).
Observed Results:
When the items slide on the ice, they get picked up by hoppers unless the item is thrown onto the west side of a chest.
Expected Results:
No matter which direction the item is being thrown from, the hoppers should pick up the items.
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Can confirm! This is indeed an issue, and affects a TON of sorting systems and item transport systems. My initial theory to this issue is that the hitbox of items is off center, potential in the direction of south east. It would explain these issues, but i have no way of confirming this idea.

In 1.16.20

Yes confirmed twice very annoying

I can also confirm. I lost 4 diamond ores and much more because they despawned in my sorting system. Really annoying

It's worth noting that at least in some cases these big circular water stream systems would not be necessary for sorting items if MCPE-38963 were fixed, because then you could put multiple filter hoppers down one row and items would not be blocked from getting collected on the first pass.

From a comment on duplicate report MCPE-92670:
Some additional information for you. It seems to be specific to the east\west axis, no matter which way the items are flowing. It the items are flowing either east -> west or west -> east with hoppers to the north, the problem exists. If the hoppers are to the south of the water flow, the problem does not happen. You can see this in the xbox capture I took while holding a locator map to determine direction. Link to the capture stored on my one drive here as it is too large to upload: https://1drv.ms/v/s!AjfuKwvMMdCpj3Un8354IPHYoDGM?e=gVbOes

Note that when testing this issue, it can be complicated by MCPE-99462.

The hoppers in big storage system are affected by MCPE-99462, MCPE-38963 and also MCPE-94491, these bugs may cause the lost of a great amount of items and the need of circular water circuits for automatics storage systems.

Anyone experienced this issue in 1.16.100.57?

Does this issue also affect certain items more? I can't get the working streams to pick slime balls or redstone torches.

@Philip Mason: that may be due to MCPE-38963. There shouldn’t be a difference based on item type.

Working properly in 1.16.200
thank you
Edit: Bug still present, one of the ways to avoid was have in all the hoppers a chest but now that made that item aren't suck by hopper.
The items sometimes get suck but the items in the water stream lost momentum and stop in middle of the stream

Appears to be fixed in 1.16.201 Hotfix

Does not work in 1.16.201 still. See screenshots 2 and 3. (there is no screenshot 1, fyi).
The hoppers are on the westside of the chunkborder that runs right between the hoppers and the ice / waterstream.
In screenshot 2 The hoppers will only suck in the item if I let the item run into a honey block (coming from the bottom left). It will get dragged along by the waterstream flowing left to right at the top (it is slow but it works). So I think the item is not in the chunk with the waterstream, as the honeyblock stops it just in time to get to the next chunk. If an item runs into a honeyblock, this 1 pixel is just enough to stop it from crossing a chunk border.
If I rebuild the stream and let the item make a U-turn into the honeyblocks, they don't get sucked up by the hoppers (screenshot 3). If I replace the honeyblocks with anvils it still doesn't work. So the item needs to be at least '3 pixels' in the chunk that has the hoppers. With 3 pixels I mean that the 1 pixel of the honeyblock or the 2 pixels of the anvil are not enough, and putting a wall there (with 4 pixels off) makes the item just land on the first hopper if the hopper can't accept that item (like is often the case in the item sorter systems we use this for).
So based on this observation the item is considered not crossing a chunk border when it bumps into a honeyblock as in screenshot 2. That is my analysis of the issue we're facing.
Coincidentally I found that screenshot 2 is a compact work-around for the item sorter issue many are facing. As the item is still 1 pixel in the water stream, it still gets dragged along by the water, be it slowly. Forgive me for adding that here, but it was too nice to not mention it.

Tested and could not reproduce in 1.16.201 Hotfix, so I am resolving this as Fixed based on comments above.
@Jack this Out: this report is about directional inconsistency, not the chunk border problem. Hoppers not collecting items from water streams on chunk borders is tracked at MCPE-99462.

The one on the west happens to be crossing a chunk border too (x=63-64), doesn't it?

Possibly so, it's difficult to tell from the screenshot alone. Regardless, this report never attributed the inconsistency to chunk borders.
I just re-watched the video from MCPE-92670 that I linked in an earlier comment, and the issue there, too, appears to possibly be due to chunk borders at Y = -1280 to -1281 and Y = - 1264 to Y = -1265. So it's possible this entire report was based on a misinterpretation from the beginning. Whatever the case, MCPE-99462 describes the bug that can actually be reproduce as of the current version.

Base on my test the bug it's solve
with all the 0.9 block the waters stream its working as intended in a single chunk.
In the past I have to use the walk-around having chest over all the hoppers of the water stream to keep the items collected but since 1.16.200 its solve and all working, thanks for the Effort.

Yep, this bug appears to only happen when chunk borders are involved now. Didn't have any issues with sub chunk borders in my testing, so thats nice 👍 Before this would happen regardless of chunk borders, and was very inconsistent.
Chunk borders affecting this is still a big deal, since borders are not something the average player will think about, (or may even know exists) when building their sorting system, but can cause their entire sorting system to stop functioning. Can't wait until this, and the other sorting bugs are gone for good:3
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