My 2 year old ultegra 6700 right hand shifter is very sluggish when shifting up. The shift isn't sluggish but rather the shifters return to its original position. I have changed the gear cable and this has helped for a while but it is back to its sluggishness again! It feels as if the spring or whatever is in there has lost some power! Is this a bin job for the shifter or has anyone any suggestions?