It's very difficult to try to help solve a problem without being there to see what is going on first hand, but there is a lot of experience on the forum board, so hopefully someone with first hand knowledge will come along and get you going. In the mean time, I think there are 2 general theoretical ways to approach your problem. 1 is if the "garbage" is large sized pieces and some unthreshed grain or seed, it is falling through the concaves too soon. Generally I would tend to blank off, or use cover plates on the first concave. (in your case, module) This should help rub out more of the unthreshed grain_seed, and reduce the size of the chaff so the chaffer and air blast can deal with it in a more consistent manner. 2 if the "garbage" is very small and light weight, and there is many cracked pieces of grain_seed, then I would tend to slow the rotor down and open the concave_modules. Sometimes an overloaded chaffer and inconsistent problems with the machines performance can be traced to something so simple as not keeping the machine full. Example: If I run my 1680 too slow in fescue grass, it will load the chaffer heavily with long pieces of straw, and the rotor cage will plug between the concaves and the grates. But if I push it a little and keep it full, those problems go away, and all I did was speed up my ground speed. Dont know if any of that helps you in your situation, but I'm trying.