posted on
May 10, 2009 at 11:01PM
If the grass is too high or wet, this can happen.
If it is too high, then you need to discharge the grass at a high setting so you can work the grass down to a workable mulching level where you can mulch the whole way through.
If the grass is wet and you are mulching, the grass may be caking itself to the sides and top of the underside of the deck. for this, you might try spraying the underside of your deck with the grass non-stick spray before mowing.
But it does sound like wet or tall grass, or both, are the problem.