How many times did you try with the whites... and was it all in a one window period of time or off and on?
My logic and reasoning are getting itchy for an answer here.
I'm just wondering if maybe someone else was selling back at the very same time you were testing, creating more inventory.
Then, the game mechanics would only allow 8 to be sold to one individual to reduce the chance of another color crash.
From what I read earlier, it appears it took more than 1 individual buying to empty a color. (5 or 6 I think I read)
If that's the case, maybe it automatically wouldn't sell more than 8 to a single player.
If that's the case also, a single player could never achieve alone what happened above,
It's an Accute Dyespiracy Attack plain and simple! (Let's hope it never becomes chronic!)