ZT2148XL Leaves uncut strips especially when the grass is tall. How do I correct this

[MarkSchmitt]

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?

 

[Carscw]

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?

Dandelions are hard to cut. They just bend over.
As for the strip of grass a few things cause this. Letting the grass get to tall and trying to cut to much at one time. Going to fast. Deck not set up right. Turning to the right.

I heel my deck. That is set the back of the deck 1/4 inch lower then the front