I have a Hyperdrive chip in my ol' Vlocity, and this issue seemed to get a little worse with it. When it's not actually feeding it will every once in a bit run for a few seconds, and it sounds like the gears are skipping. Not all the time, just a few times until it seems "satisfied" with something.
Like nerdcore says, I assumed it was keeping tension on the stack.
Not really a big deal, just a little annoying...
Don't count me out until you see the box being lowered into the hole...