Is there an easy way to straighten the leather back out flat? Any one have a secret technique other than replacing the leathers? I have also found that a gapped leather can also cause the adjacent reed to buzz before seating.

seems like you could heat one side or the other
but i wouldn;t know which side to heat
you could experiment with some non-accordion leather
if you needed to heat the back side, that
would be harder
but not impossible

or just remove it, fix it somehow, with heat or
manipulation, and reglue it

wle.

Here's a traditional fix...spine the leathers. You can do this by slipping a reed lifter or other thin metal strip under the leather, and using a pointed but not sharp awl to scribe a line down the middle of the leather. This gives it some structure and helps keep it flat. The leathers on the Martin don't look bad to me, though.