Hello Andi! Welcome to the Router Forum. Glad that You found us. I have a Craftsman plunge. and their is a small lever to lock position on it. I have had the screw that holds the lever in place work loose, I didn't''t know at first, what happened. I tightened the screw a bit and fixed the problem. I would guess that the knob has small splines in mine. Hope that helps. Also, it You can give us model, it may be something that has a quick fix.
John 3:16 Please fill out your profile, It helps us to know you better