I'm a firm believer in hanlon's razor. Never attribute to malice that which can adequately be explained by incompetence. Clumping means it was likely exposed to moisture, and there are dozens of ways for it to accidentally happen. It could be parts of an old batch that have been sitting, there could have been a spill or a leak, or it could have happened in transit. I'd suggest multiple people test the SN they ordered, and if it's still shows up as good then I'd say there's nothing to worry about. Only if there's a lot of fake SN being shipped is when I'd say it's a scam.