This area of ripples appears common on most of the Boeings - I stand to be corrected but it appears to be a non pressurised area - side of the wheel bay, body/wing join, not that structurally critical?
Again on 707, 737 and 727 it was very common forward of the E-F posts in front of the cockpit and pressure bulkhead - as well as on the 707 rear area like the 747 pic and like the 757?
Be interested on some more indepth qualified input?