Shimano STI

I have Shimano STI 9 speed shifters (Ultegra) and the right shifter seems to have an extra
position. If you move from the large cog toward the small all the steps are normal until you are on
the 12 (small cog). Now if you press the lever again the shifter has one more step. The derailler
doesn't move as the outer stop has been reached but the shifter cable is now slack and to bring
everything back to normal you must move the lever like you were shifting up one position. When you
do this everything works fine. Also the cable moves about 50% more on this last step than on the
other steps. By changing the cable length you can actually use that last stop for the 12-13 step
but because of the extra motion you get a double shift from 12 to 14 and after that everything
would work O.K. The shifters are new. I seem to recall a system that would let you shift the chain
past the small cog to a hanger for wheel changes. That was a long time ago but this would do this
if the derailler stop was not there. Bottom line... The shifters work fine except for this extra
step. George