For the past couple of weeks my Walker has been leaving random grass blades standing up. It is not really bad, but it does bother me. When you look back after you make a pass, you can see random blades standing up. It does it in short grass, tall grass, moving fast or slow. It does it in all kinds of grasses too. My blades are sharp and it does it with any of the 3 sets of blades I have installed on it. Any of you Walker owners ever had this before? Thanks for your help.