I'm pretty much sure what the answer is but here goes.
All 105 (9)sp components with a 105 external 50-35 Crank.
I ride a smaller bike so the chainstays are short. On the 34-12 rings (small, small) the chain catches on the pins on the 50 ring. If I shift up to the 13 the issue goes away. Obviously the chainline has changed.
Has anyone had any luck with shimming the crank out a mm or two?