I'm having a minor issue with my Shimano 105 rear derailleur and was hoping someone here can offer a solution. During yesterdays ride, when shifting up (on the cassette to a lower gear) to a middle gear on the cassette, the gears would click but the shift would not happen. If I double shift up then shift down (on the cassette, not talking gear ratio) one gear, I got into the gear I wanted originally. The higher and lower sprockets engage perfectly every time. It's just the middle sprockets and usually only when shifting up, not down.. but no always.
I don't know what would cause that issue for me. I know how to adjust if the shifters don't make the outer sprockets on the cassette but this is in the middle. The cassette is very clean, as is the chain and it is properly lubed. Neither chain or cassette are worn since they are almost new (maybe 1,000 miles). Nothing is bent or misaligned as far as I can see.
Any ideas?