If I have an Mk1 (for example, the same happens with other mk2, mk3, etc) pipe between 2 chests and I put an active supplier module set to keep 16 pieces of dirt and right-click it with a crescent hammer so that it supplies one chest, it will continuously supply the chest until it fills up.

This is a photo of the setup:

This photo shows how the Active Supplier Module is configured:

This photo shows how the supplier keeps supplying the chest.

1 chest per pipe.

I know that solves the issue, but it shouldn't do what it does if you connect 2 chests to one pipe.
For example, sometimes you don't have space to place the pipe where it is not between 2 chests.

Then use a pipe plug, or a facade on the side you do not want to connect to the chest.

there is also the disconnection upgrade from LP itself

they might be cheaper but look kinda weird on the LP pipes, i've also noticed that on sometimes the routing doesn't take them into consideration, sometimes it sends an item that way, then said pipe realised it can't go that route due to the plug and sends it back, usually heapens after restart but it's rare

That is true. I usually use covers when I can.

@ivangouba Can you reproduce with a disconnection upgrade on the other chest, or without the chest?

I have not tried with a disconnection upgrade, but if I remove the second chest then it works perfectly.

Then it is working as intended.

Forgot about that. Plugs are cheaper so I rarely use the disconnection upgrades.