Items in minecraft item filter stacking

Question

I recently built myself an item sorter in my Minecraft survival world. Upon completion, however, I discovered that the items in the hopper named 'placeholder' were stacking inside the hopper which made room for other items to flow in and break my item filter. I have made an item sorter before just never with a water stream. I attached a video to show the problem. I assumed it was a bug but when I asked the folks at the Minecraft bug tracker they seemed to think it is an error in my Redstone.

Minecraft Java edition optifine 14.4 OS: Windows 10

Answer 1

What I've found is that the sorters work best if you keep the placeholder blocks at 1 per slot, and increase the item you want to sort up to 41.

With the setup you're using, the redstone signal coming from the comparator can easily increase past the amount needed to open the hopper below. This makes it so that the hoppers on either side will open, dropping your placeholder blocks. If the signal from one of the sorters gets big enough, it will start a cascade effect through your sorters, and they'll all start dropping the placeholder blocks.

Answer 2

You didn't show us the downstream hoppers. Nor did you show us the back of your sorting system.

The blocks you put in, are likely getting loaded into a chest downstream. Because of that, you are getting an overload signal in your dirt chest. The dirt chest drops 2 items, and the prismarine starts filling it in towards the end.

To confirm this, add a screen shot of the redstone on the backside of your sorting system, and screen shots of each of the sorting hoppers in your system.