I bought an Exmark 21" X Series unit in the spring. I like the unit very much but I've been having some issues with the machine leaving "stragglers" when I cut at 2.5" or higher. The problems seems to go away when I drop the mower to 2" but the cut is way too short. The unit has the multipurpose red blade that was brought out last year and it's kept sharp. I've had some complaints from customers so I was wondering what can be done to correct the issue? Anybody have any ideas?