I have never had that problem, but I've heard of it often. Some guys ream the hole as a routine pre-assembly process. We also sand the link balls to get all of the flash from them so the link has NO drag. And check the width of the head compared to the width of the pair of blades when they are assembled. I have had the blades fit tight against the sides of the head (blue aluminum head). A little sandpaper fixed that also.
Soloboss