Who knows, maybe all his wheels are zero dish wheels (which of course do not exist for symmetrical frame based bikes which 99.99% of us ride.)

I kinda wonder too if the frame in question has a bond that has come loose or slipped. I've seen it happen on a late 90s Vitus? - and you couldn't tell with a cursory look cause it somehow looked clean even when slipped. (Left chainstay into dropout.)

Either way - when trouble shooting frames:

1. Properly dished wheels.
2. Dropout alignment.
3. Frame alignment check / Fork alignment check.
4. Then elsewhere....including fixes.

Jumping to #4 without any dead obvious "wrecked exotics" like damage / oddities is not how you go about stuff like this.

=8-P