Which Groupset?

That was my thought.

There's plenty of stuff that can flex between your foot and the power getting to the tarmac.

Play in pedal bearings.
lose crank arms.
lose crankring bolts.
worn freehub.
spokes.

To name a few. All of these would flex umpteen times more than a chainring, or crank arms.

tried and tested all..new pedals tightened after wear in period, crank arms checked, BB checked for any play, all chain ring bolts checked (had this before on other groupset thought it was BB but then found a few loose CR bolts), new wheels and spokes checked/after wear in period.

No it doesn't effect performance too much but it's sure annoying when soon as get going hearing chain rub on Front D. Maybe it's just SRAM cranks they do have a slight rep for flexing as I don't get this on my Campag groupset.