I roast 1 - 1.5 lb batches (smaller bean size = bigger batches), and although the beans move more slowly at first, they're all moving right from the start.
I've not noticed many, but there are always some crispy critters. I sorta figured them to be hollow beans, maybe from another crop or batch that got mixed in at the coops. Whatever, since there's so few I don't bother picking them out.
BTW: This problem seems to occur with S/O beans, more than quality blends. The Red Sea Blend I roasted last had no crispy critters that I saw and ditto for the Monkey Blend from SM's I roasted last month (I keep roasting logs with that sort of minutia recorded - can you say
ANAL boys & girls?)