The crash of May 19th caused some extreme price dislocations in the spot market, with a huge spread opening up between the Coinbase spot market and Bitstamp and Kraken.
Prior to, and during, the violent correction from $38,000 to $30,500 the USD spreads remained relatively low. But, when examining the spreads between the euro pairs at these exchanges prior to the crash, it is evident that the Coinbase pair traded at a sharp discount, possibly foreshadowing the turmoil and liquidity issues to come.