A failed insulated-glass edge seal allows moisture into the sealed cavity.
The short explanation
A failed insulated-glass edge seal allows moisture into the sealed cavity.
What to compare
Compare location, timing, weather or operating cycle, then open the matching Living House layer to see the plausible routes.
What would strengthen the explanation
A repeatable trigger and a physical route through the nearby assembly are stronger than appearance alone.
Next step
Document the original condition and choose the least destructive check that can separate the leading explanations.