Peugeot Competition from the late 1990s with horizontal dropouts. 2006 Campy Chorus. I finally got around to removing the wheels, rings, cogs and derailleurs to give them a good cleaning, and now the chain drops off the small ring when I gear down to the last three cogs. You can see out of line the cogs and the rings are.

Thing is, the rear wheel is positioned perfectly in the middle, and the axle is hard against the back of the dropouts on both sides. I'm fairly certain that I hadn't previously rotated the wheel to line the rear cogs up with the front rings, as I've never had chain-dropping before and thus wouldn't have even thought to check for in-lineness. Could the seatstay-chainstay be out of whack? I'm a bigger guy, and I carry groceries in the saddlebags sometimes.

Or what?