friction adjustment tightened. It's an old bike so i can't expect greatness.
Mox, if left untouched, it can shift from the biggest, down to #2, then down to #3, then down to #4. No amount of adjustment or overcompensation going to save me from 3 jumps....
Oh, and on second thought, you're entirely right about cable stretch, but still this is too big of a gap, I'd think. And it doesn't make sense why it would only happen while mashing.
I just greased my cable guide on the BB and i'll hope for the best next time I'm commuting...