Mowing 12 high grass at 3.5 yesterday the Z-master was leaving a strip down the center of the middle blade cut area that was partially cut. The two outside blades were doing fine. Conditions were really wet. The grass was not of lawn type but a meadow that gets mowed a few times a year. Did not seem to matter how slow or fast I went or how high the deck setting was. Any reason for this? Would wrong deck pitch cause this?