I am having an interesting issue with one of the flippers on my quick draw. The flipper works fine for the first several games, then it will start sticking and will not return consistently to the down position. I rebuilt with a PBR flipper rebuild kit as I do all of my machines. When cold, if I manually test it, it works perfectly, no sticking, seems to be adjusted properly, the spring return is crisp, etc. Any ideas what to look for here?