the fading is certainly fact, how it happens is uncertain and that one case out of he box seems rather uncharacteristic and needs clarification e.g. maybe it was a displayed model he picked up from eBay or GoHasting etc? I would not quite use that to dismiss any theories just yet without more clarification.
oh is the fading in everyone's MIIIBD uniform back and front? If there are exceptions and different levels of fading occurs then it is likely an external factor e.g. light. If it is fading evenly in all cases then it's in internal factor e.g. chemical. The only part that is then hard to explain is why are there cases where it is not fading at all
This is as much of a mystery as the leaky rubber on DX02