Blakmax suggests the bonded doubler is not a repair, but an attempt to detune that panel, as if there were a already known acoustic/resonance problem there.
I seem to concurr
That said, Old Engineer might be onto something! But it may be more to do with varying pressures, than an absolute exterior reduction. At some fuse attitudes and Mach Nos, it's possible slight (but long term, sustained) buffeting in that area, may have contributed.