There are a number of factors that can affect quality of cut, some of which may be turf conditions. Turf conditions such as excessive thatch, "sponginess" or attempting to cut off too much grass height may not always be overcome by adjusting the machine. It is important to remember that the lower the height of cut, the more critical these factors are.
Remember that the "effective" or actual height of cut depends on cutting unit weight, cutting unit accessories and turf conditions. Effective height of cut will be different than the bench set height of cut.