Originally Posted by
RandomTroll
I lowered the front derailleur 4mm and solved this problem. I don't remember raising it: could it have worn in such a way to make shifting from the small to the middle difficult?
Aha! If the FD is too high (Shimano's recommendation is that the outer part of the cage be 1-3mm away from the big ring when it is right over it), you can have similar problems to RDs with too much "chain gap" (jockey pulley a long ways away from the cogs) -- control isn't as good, so you need to overshift to make the shift happen.