The gif will explain it better than i can but if you ctrl+drop a whole slot(more than a stack) from a dank over a vanilla hopper, the hopper only picks up one full stack and the rest gets voided. Im assuming it has something to do with how the items are clumped together in to one entity(which is great ofc).
tested with just JEI and dank storage v 1.16.5-3.20 and no other mods installed. forge version 36.2.30.

gif of issue, first dropping the slot on to the ground a couple times then dropping onto a hopper. Can see the 3 stacks of stone turn in to one stack inside the hopper.
https://gyazo.com/ec814e9e81420a7dc00effdcc57b610b