I got close to that amount of crud in my first (only) oil change. Have many times you changed it before? Looking at the pm-727m's blueprints It appears the coarse/fine feed shaft doesn't go into the gearbox. It goes below and to the back of the quill where those teeth are cut in the back of it. If you look under the head behind the spindle, you can see where they engage. If there is slop up and down on the quill and only during fine feed then there might be an issue with the worm gear engagement. Maybe the clamp knob is not in tight enough? Gunk in the worm gear? To me , part (3) and (21) are worth looking at.