I just had a longish talk with somebody at issuer services at OTC Markets. Obviously the problem is that if a market maker asks them to trade a Grey stock unsolicited, their compliance people don't bother asking any questions about who the MM's client is. Nor do they look into the company itself, evidently.
So I explained CRGP's sordid history. The guy told me that retail can't trade stocks that trade on an unsolicited basis. That's not my understanding, but in this case it seems very likely that one of the noteholders from 2015 wants to dump the rest of his stock. None of them managed to sell all their holdings back in the day.
He seemed to feel the volume was "unusual", and said they'd take a look at what's going on. I suggested he do some reading about the litigation. He said maybe he'd call FINRA.