You've probably got a loose guide in the head. You'll find out when you pull the springs for seal replacement.

But, if you wanta believe in the "miracle in a can" stuff, well then, for just the small price of $200 US (cash, small denomination bills only) then I can "double your I.Q. or no money back"! Don't wait! There's thousands of people, well maybe, hundreds of people, well okay then, my third cousin Joe-Bob, just lining up for the chance to get smarter! Actually he's lining up 'cause he thought there was free beer but no one has told him different.