I've got a 2013 Giant Escape 0 Hybrid with a stock 10speed Shimano Deore rear derailleur. My wife was riding the bike the other day, and somehow managed to shift in such a way that it popped the chain off the rear cassette and jammed in between the sprockets and the spoke protector. Luckily no damage was done.
After putting the chain back on, I put the bike up on a stand to check/tweak the derailleur alignment. The small sprocket and the large sprocket are properly aligned. I can shift up and down with almost no problems; I seem to skip the third gear.
If I take the rear wheel off and click the derailleur, I only count 8 clicks; not 9.
I'm not sure what that means. Nor am I sure how my derailleur can be properly aligned on the smallest and largest cogs, hit all the shifts except for one, and yet miss an index.
Is this an alignment issue? Is there a problem with my shifter? Is my derailleur whacked out of position? How/why could I be "missing" an index?