We were combining our oats today and when in got really hot and dry around 2 p.m. we started getting a very dirty sample in the tank. After trying different settings, we realized that the left hand side of the air box between the sieves and the fan was plugged with oats. We cleaned it out (at least that is what it looked like) and within 10 min it was plugged again. I am running my bottom sieve at 3/8", top rear at 5/8 and top front at 1/2". Fan speed is 690- 740, and rotor is 3.5 at 700 RPM. Oats are running about 145-160 bu/ac, 21' swath at 2- 2.6 mph. I looked at the other post regarding rice and it was dealing with a 7120 which had features that a 2188 doesn't. Any help where to look/ what to do would sure be appreciated.