I experienced this withdrawal issue last time I withdraw my signature payment but I'm not open a ticket and wait for several hours and when checking my withdrawal status its already sent, maybe this happen because of bitcoin transaction delay.
As a signature payment, it was expecting a delay because that is manually checking under your account and for possible abuse happen.
Not just by a transaction of bitcoin, the Windice.io team ensure the activity under your account, it should don't have abusement. It's okay to wait under 24 hours they had a right to check in every transaction for the sake of their company.