Coinbase buys instantly about 90% of what you "buy" when you do, and buys the other small bit when the money actually comes in. Thus, if a large price increase occurs they would take an overall loss on the sale due to the rise in price THUS they lie to you and say "flagged for fraudalent transaction" or some other BS to prevent a loss. Really wishing someone would sue them for this obvious and blatant lie and act of fraud against customers.
Do you have any proof?
Its pretty obvious thats what they do. They say in one of their FAQ sessions, about the 90% or whatever. Find me someone who made a purchase with them and got canceled after the price went down. Funny that no one has ever had a purchase get canceled due to "fraud prevention" after the price goes down a significant amount.
I used them multiple times in the early part of the year when the price of Bitcoin was skyrocketing. At that time there was no instant credit so I had to wait out the multiple business day hold but never were the transactions flagged for fraud. I'm not saying one way or the other what's going on because I truly don't know, just telling you my experience.
Maybe it has something to do with the credit check company they use or certain people's credit history?