Pete C. wrote:
Doug Miller wrote:
....
Both you and the OP have got the idea so firmly fixed in your heads that a
heat source inside the wall is the only possible cause of this problem, that
neither one of you is the least bit willing to entertain any alternative
explanation.

No, we have objectively analyzed the available information and concluded
that an internal heat source is the most likely cause. ...

I still think the _most_ likely is an external heat source...

Why OP hasn't opened the wall to confirm/deny the indication of an
internal heat source is, I think, owing to being uncertain enough of the
repair process that he thinks cutting into the sheathing is a much
bigger deal than it really is.

Where, in fact, the bigger deal is the possibility that Pete is right --
I really don't think that will turn out to be the case as I think the
amount of heat required to produce this external damage if it was
arcing-generated would have shown up w/ some electrical anomalies
although that certainly isn't absolutely required.

The solvent problem I think can be discounted as being too far removed
in time and frankly the damage pattern just doesn't have the shape for
that to have been the cause unless it were a misdirected spray gun blast
and the reported application was rubbing w/ a rag instead...

Only when and if OP actually finishes an investigation and reports back
will anything else possibly be learned...

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