I have a 2005 Gravely ZT2148XL. I have always had issues with uncut strips of grass, especially this time of year when the grass grows too fast to keep up with. I keep the blades sharp and have even installed an additional set of Gator blades on top of the stock blades. I figured 4 cutting tips per spindle is better than 2. This didn't help this, I still get the uncut strips. I can even cut over tall dandelions and they will not be cut. Yes the cutting edge is correct. Any suggestions on how to eliminate this issue?