I have a storage system where one part of it leads to a bunch of black hole units (from industrial foregoing), and another to just random chests. I have it set in the responder chip's preferences to where I want all the cobblestone going into the black hole unit. However, when I throw in, like 2 or more stacks of cobble in at once (2 at minimum), 1 of the stacks will go into the black hole unit, and the other stack/stacks will zip right past it into the filler chests. When I tested this on a creative world, it seemed to be that the items could not transport more than a full stack of 64 items at once. Once that 64 is sending off to the black hole unit, the pipes seem to think "ok, that 'chest' is full, on to the next one", and ignores it until everything is done. When I tested this in a world where it was ONLY connected to the black hole unit, all the stacks of 64 would move single file, only proceeding to the next stack if the first one was properly within the unit. I even tested this with stacks of 8 items instead of 64, and sure enough it worked flawlessly. This happened on both version 4.9.1.92 and on the latest version, aka version 4.9.4.120. Idk if this is a compatibility issue or not but I hope this helps you look into the problem.