Interesting. The left-hand end of that specimen has a glossy sheen that initially made me wonder whether it was PE, rather than PVC, but is probably migrated plasticiser. PVC has multiple possible degradation modes such as plasticiser evaporation, hydrolysis and dehydrochlorination. How fast any of these processes occur depends on the material composition, temperature, environmental exposure etc. The processes interact and can be self-catalysing especially if the exudate cannot escape easily.
The plasticiser used in the batch of red insulation might have been of unusually low molecular weight, resulting in accelerated migration and evaporation, despite performing to spec during manufacture. Unlike cables with green goo, there won't have been any reaction with the conductors because they are tinned (the extreme loss of phthalate in green goo cables is usually the result of the antioxidant.)
Is the red insulation or the inside of the sheath sticky? Does it smell of anything?
