Take a look at the picture Vid posted, there needs to be a gap where the picture shows a gap. This ussually happens when the clamp that holds the flipper shaft gets stretched, ussually from cranking the piss out of the clamp. A good suggestion is to lightly sand the flipper bat shaft where the clamp comes in contact with the flipper shaft. Sand parrallel with the flipper shaft. Most likely too late for your situation, but if they are streched and you do need to rebuild, try sanding the shaft during your rebuild instead of the suggested "crank the piss out of it" method.