I had a problem with that 2 seasons ago and I don't really know if it was from the front shoe being froze up or the bushings being out and breaking the bolts on the back of the sieve that holds it to the shaker rails. So this year I put new bushings in to fix that and made sure I got done before the snow flew so I had no problems. The other thing you could try is moving the clean grain to the faster speed.