Wow, yeah, that is a big deal. What a weird mistake.

Having as many “good people” working with them is about as positive as we can ask for at the moment

When a friend of mine decided to join the Army after college, this was his rationale. That organizations like this need people like us in it. That explanation has stuck with me for a long time.

CBP does make a lot of weird mistakes. And just having documentation doesn't mean they'll believe it, either. I spend a lot of time at work resolving fraud concerns (often against citizens, as you said), and most of it is only raised in the first place by CBP drawing conclusions only to support them doing whatever they want with the person in front of them, and then the record will be there to confuse the rest of the government forever.

Good luck with your process moving forward!