I have a Shimano Tiagra 4700 10 speed group set.
I can only get 9 gears working - the shifting is smooth with no jumps but one gear is missing, either at the top or bottom depending how I setup the rear mech. If I disconnect the cable from the rear mech and then hold the cable by hand I can feel the shifters click through 8 times - one click too few!!. So the problem seems to be in the shifter, as if there is something blocking the shifter from turning that last slot.
Could it be a faulty shifter? Is it easy to take them apart to check?