Mod Version: 0.2.0+1.19.4

It is common practice to stack side facing hoppers for items from a higher hopper to go to the side when not pulled down by a lower hopper. You demonstrate this in the small sorting system on the mod description page.

I am currently seeing an issue where, when the lower hopper is filtering any two items (melon slices and carrots in my example) and the side-facing hopper above is filtering the same two items, if the lower hopper becomes full, the upper hopper refuses to push items to the side into any container.

I've experienced this with the lower hopper facing in every direction.

I think I'm having the same issue you're describing, this layout doesn't work properly:

Can confirm, this doesn't work as expected in 1.21.1