How do you remove the center control knob? I believe it is threaded, but can't hold the shaft from turning, unless it is accessible by removing the top cover. The center knob just turns and does not engage to turn the outer bezel ring. I can turn the outer ring manually. Thanks!

It is the center timer selector/on/off knob. You pull the knob out to turn the machine on. You push the knob in and rotate to select the cycle you want. The knob does not engage when you rotate it to select the cycle. It spins freely.

I just pried the center knob off. I is held on by the inner knob plastic clips. The problem was the inner portion of the two piece knob center shaft broke allowing the knob to spin freely. I am ordering the center knob replacement. P.S. I had to use needle nose pliers to unscrew the broken piece if the shaft.