Having a major problem tying off my last cross on a Babolat Aero Drive. I can't get the string back through any hole to tie knot. Hours spent using awl, wd-40, grease, needle nose pliers, etc., and nada. I am a rookie with around 100 frames under my belt. I can get an awl through but it seems to close down. Using dura-flex 16. Any ideas?