Looking at the photos of the chainstays, it looks to me like the Driveside chainstay is bent, curved outwards going towards the dropout, in contrast to the Non-Driveside chainstay which looks like it's straight from the bottom bracket to the dropout.
Remove the rear wheel and measure the dropout width. Looks to me like someone tried cold setting the rear dropouts and one chainstay bent while the other didn't.
Last edited by RoadGuy; 02-22-15 at 01:16 PM.