When I worked at a book, we never cut off losers. One of the reasons why I quit is because management went out of their way to try to deny any big payout. They'd pour over everything to deny a payout to a winner. It was sickening. Did the player ever use a VPN? Were they betting on smaller leagues? If it was a casino player, we'd ask for player logs from the vendor (every single time). If the platform tagged them as 'High Risk', ban.