Jaidan

Just had this issue happen to me. Interestingly enough it was in a bedrock 1.20.73 realm and visible to all players. Could even place blocks inside it including chests that were still functional. 

It happened in a replication of this bonemeal moss farm https://youtu.be/uvA9moY0tf8?si=rpnGJZ3xgEdsPiuJ in the centre of the machine where the moss blocks get squashed - not directly next to the piston. 

Mathew's explanation of accidentally glitching out the chunks does still make sense for this case however, as the cause of this was (presumably) having an Xbox turn off while afking at the machine. The only possible fix was to right click/left trigger/L2 on each "block" with an empty hand.

However... Bit of a problem. That only fixes the issue client side. Meaning it just turns into an invisible version that reappears after you relog. On top of that, the interacting with the "block" with an empty hand fix no longer works. Pistons can push blocks into the "block" but once a block is inside it, that block becomes immovable in the direction that the "block" was originally being pushed. You also can't place anything on that side of the "block", so an offset hotbox makes sense. 

Honestly don't care if it can be patched of not I just want a way to get rid of it so I don't have to rebuild the farm.

(Sorry for slow reply/update)

I was unaware of the cooldown or unusual behaviour regarding multiple stacks sitting on top of a hopper. The cooldown would explain the issues I was having with water streams as I was using a observer clock to dispense the items into the stream. I do not believe they explain the issues I am having with unreliable item sorters however.

I have a piglin trading farm with 11 piglin. The drops fall into a hopper line (yes I know they produce too many items for that it was an oversight on my end). The hopper line then passes over the standard style of sorting system. On occasion, items are able to completely ignore the sorting system and pass right through to my final chest for non-stackable items. 

In the portal powered gold farm I made, I used three separate sorters per item (ingot, nugget, flesh) to get around the issue and have since seen items make it to the third sorter before being stored. This is despite none of the storage on any of the sorters being filled and using a hoper line that only moves one item across at a time. In both situations it has occured whilst standing within the same/adjacent chunk to the sorter so it will not be a problem with unloading a chunk while an item is being sorted. Just waiting for an item to make it through all three sorters and clog up my auto smelter for the gold swords.

I will admit though, it is occasional (one in every couple stacks) so I wouldn't be surprised if it is due to some of the performance issues you can get on bedrock (especially since I'm on Xbox one which I've found to struggle with 150+MB worlds and multiplayer)

I've noticed beds in your inventory also drastically affects performance while in the inventory (Xbox one S, latest version)

(reply to Helmut Joaquín Pfeffer García's comment)

if you're talking about the two comparators next to each other on subtract mode you can do a temporary fix by putting two extra comparators on the back and side inputs of both comparators. It makes the circuit bigger but it's the best you can do until it gets fixed

(Testing done with output facing south on XBOX One S)
A second comparator used as a buffer can act as a temporary fix to the comparator breaking from two inputs from the same source. In builds that require specific input strengths you could just put a comparator on both inputs to work around the bug (Note: some things cannot be fixed using this method such as anything limited by size e.g. comparator clocks, comparator XOR gates).