Ran one for quite a few years and never had that problem.  How fast are you driving compared to chain speed? We chopped drought corn in 2012 and didn't have issues driving pretty fast.  Is your gathering chain tension correct? Not all stretched out and jumping drive teeth? Your stalk discs are set right, and are turning, not slipping somewhere? Those heads should feed in almost any crop conditions. 
Edit to add: I'm assuming its a 3pn head.  If not I have no idea.