RetiredF4
How about moisture being the cause for a short?
In between lines it was a possible cause for the ANA event. The fix with the firebox talks about improved insulation also against humidity.
Does the no metal hull behave differently concerning condensation and causes humidity at places not expected?
To expand that a bit since there now appears to be battery related incidents with 2 very different batteries, one of which (ELT) has a significant problem free service history the question can be what is different about the 787 compared to prior design.
A couple of obviouse ones with comments.
Significantly higher "electrical content"
Certainly a factor in the main battery issues but hard to see why this would affect the ELT.
Composite construction:
Possible thermal environment changes, hotter baking in the sun etc.
Non conductive, requires explicit ground (return) paths, improperly sized/damaged these could induce unexpected voltages.
Possibly worse ESD environment.
Different cosmic ray shielding properties?
Particles that would have been blocked by metal may pass through. (Bit of a reach, pure conjecture on this one...)
Outsourcing:
Again possibly a factor in main batteries but the ELT is (so far) problem free on other types.