might be a little late but is probably coming from your precleaner as anything that drops through goes directly to the grain tank. Yours may have sprung open a bit and straw is spearing through from the grain pan below the walkers. Seems no matter what you do, you cannot get those fins completely closed as there are always a few that are sprung a bit. Precleaner of no use to grain farmers, I wish JD would offer a grain pan option to replace the pre cleaner sieves to small grain farmers.