I am extremely embarrassed to be asking this, but I'm at a loss. Awhile back one of my knobs from my Jazz fell off and it is so loose that it will not stay on anymore. It is a 2003 MIA Standard if that makes any difference at all I have tried standard and metric allen wrenches to no avail to try and tighten the black plastic knob. What am I missing here? How are these knobs supposed to be tightened? I attached some pictures so everyone can see what I'm talking about. I apologize for the question, but any responses are greatly appreciated.