is your head new or some years oldIJ ours did fine when it was new, then after about 2 years our did the same thing. i tried roughing up the edges with a welder on low heat to give the flighting some bite, it helped till i got in some vines and the it just rapped up. then this year we decided to swap sides with the knives_rollers on each row(they are not reversable but you can take the ones off the right side and put them on the left and vice versa). this has helped so far jerk the stalk through better. it puts the sharper edge where it grabs more. but when we wear that edge down we will have to replace all of the knives. have in the past when we had a 6 row took a welder and roughed up the edges of the knives also.