My posted model is based on 3" diameter knob with 1/4" roundovers. Following your suggestion, I created a test piece and got similar result as shown below. First, I created a large circle with 100" radius (with 100s applied) and inserted smaller radius of ~25" (with 100s applied) at the intersection of red axis. Deleted lines to create a notch in bigger circle. Added ~15" roundover at the intersection. Extruded the surface to desired thickness. Applied smooting tool to the model. Created rectangle along green/blue axes and then created ~15" roundover. Applied follow-me tool along top edge. As you can see, it's still producing holes. I've tried several methods I can think of, but no luck.
My goal is to create a knob and scale it to various sizes ranging from 1" to 6" for 3D printing.