I have a lazer z and when i cut medium up to heavy grass it leaves 3 streaks down the middle of the blades. When i cut really thin grass it does the same thing no matter if i have new blades or sharpened blades. I have to go over it two times and it cuts clean. It doesn't't matter if i am cutting at 2 inches or 3 inches or higher or lower it still does the same thing. had been doing it since it was new. thought it was fixed for awhile but it started it again. i bought it in October of 04 and had two seasons. very frustrating any questions. I have used all kinds of blades from low lift to high lift even mulching blades and it does the same thing. Any suggestions is appreciated.