Right brifter releasing two positions from 1st to 3rd
Right brifter (2003 tiagra) is releasing two positions from lowest gear (largest cog) two positions down to 3rd gear. The RD is otherwise well-tuned - note that when it goes down two spots, it is in fact two index positions, not just skipping a gear due to being mistuned. In other words, I can shift gears from 1-3-2-1 all day long, with all the shifts completely smooth. However, it takes more force than normal to do the 1-3 shift than other upshifts.
Any ideas? I'm not sure when this started, simply because I spent 2 years with a bent hanger that prevented me from getting into 1st gear. I discovered this when I bought the Park DAG-2 and straightened the hanger.
Is the brifter just worn out? Clearly this isn't fatal, though I was hoping to sell the bike in question soon.