I have a 1998 Leadwell v40 with a mitsubishi meldas 50 controller. Today it is not letting me put a tool into the spindle. I have no idea what the deal is. It looks like the clamping mechanism for the retention knob is not staying down. It used to stay down as long as you held the tool unclamp button. Now, once you hit the button it comes down and goes right back up, even when you keep the button pushed. Any help or ideas on how to fix this problem would be greatly appreciated.