This is a common problem for sportsbooks. It's actually gotten a lot better because most offshores have sped up their bitcoin payouts. But it's still an issue at some.
The book will "process" the payment, but all that means is they send it to the 3rd party for them to actually process. This can lead to a delay of several hours to several days. If the price of bitcoin goes down during that time, you lose.
What is immensely frustrating is that these sportsbooks don't realize this loss is their fault, and they need to own up to it. If they don't like it, they should improve their payout process - get a better 3rd party provider and/or negotiate quicker agreed turnaround times.