the concave in my new cr doesn't seem to calibrate correctly. dealer sets the concave at 1 inch like the book says and hit calibrate. open or close the concave and then return to the 1 inch setting but the concave is not at 1 inch. can be anywhere from 3/4 to 1 1/8. have replaced the potentiometer but does the same thing. when you close the concave to the stop where the concave is at about 1/8 the display will say 9/16 or so. it varies but never 1/8. any ideas? how can you calibrate something at only one point? shouldn't you be able to tell it where zero is and where all the way open is? any help would be appreciated.