I've got a 1 year old Iron Horse Glory (mare I think with an Ultegra 9 on the rear. When shifting down to the granny gears, I frequently get a kick back where the chain initially moves to the selected lower gear, then quickly drops back to the higher gear. It usually happens when shifting from 2 to 1, but sometimes from 3 to 2. If I attempt the shift again, it usually works fine. I can't seem to find the correct spot in the barrel adjustment to make this go away without introducing other shift problems. I have about 600 miles on the bike.
Is this just something I need to learn to live with or can it be adjusted out?
(Or perhaps do I need some spurs on my shoes to convince the bike to do the right thing?)
Another thing that can help sluggish shifting is to clean and lube the cable and housing. Especially down low where the cable runs under the BB and to the rear housing, it can get gritty there pretty easily. Also clean and lightly lube the pivots of the rear derailleur.
Dirty corroded cables would be my guess but something else you can check is making sure you have all of the cable out of the shifter before attaching the cable to the derailleur. Shift to the smallest cog, detach the cable flip the small shift lever a few times while pulling the free end of the cable. Pull the slack out while re-attaching the cable. Then adjust cable tension as needed.