Looks like a 'fails safe' structure that has failed!!!
The Back to Back structure is a typical 'fail safe' design.....only one is meant to fail before discovery of the defect.
I would look back in the archives if I were EI....there was an issue with Aileron PCUs around 1995-1997 where the servo control valves were incorrectly machined, causing excessive loads on the PCU body, the ends used to come off if they failed. This may have caused the start of the fatigue failure? Who knows? Lots of ADs around that time on them....(used to assist with trying to control the replacements, when AI could produce spares)... And yes same problem on A340......