I'm (pretty) sure this is a result of them using MongoDB. A friend of mine also accomplished a double sell (BTC -> USD, -1x credit on the BTC but +2x on the USD

I'm (pretty) sure this is a result of them using MongoDB. A friend of mine also accomplished a double sell (BTC -> USD, -1x credit on the BTC but +2x on the USD), he ended up keeping it and never hearing from Coinbase.