re: MuscleChuck - Quick Change Router Chuck

I've had a Musclechuck on my CNC router for several months now.  I love how easy it is to make bit changes now but I've been having a problem lately.  It is almost impossible to get 1/2" shafts to slide into and out of the chuck now.  I have to insert a small screwdriver into the gap that closes when you tighten the screw to wedge it apart enough to get the bit to move.  Even then, I have to pull/push pretty hard to get it to move.    I have tried it with several bits, both cheap and expensive bits. and it happens regardless of which one I use.  Caliper seems to indicate that they are exactly 1/2" in diameter.  Even the 1/4" collet slides more difficultly than it used to, though I don't have to pry the jaws open to slide it in or out.  

 Have any of you experienced this issue? I guess I am going to have to take it off to see if there some build up or something inside.