Originally Posted by
HillRider
+1 on the cable friction possibility. Also, did you check the limit screw settings and set up the rear derailleur cable tension properly? If this is your first excursion into index shifting, there is a specific procedure to make it work properly. Done right, it is very reliable.
It sounds like cable tension to me also. I could not adjust at the levers on the EF-51 while riding and will adjust today on my stand.