They tend to do that if you win they reduce the amount of stake amount you can wager with for that market.
It is bad thing to do.
They did have an email they sent out yesterday saying if you would like to wager up $100,000 on the euros you can do that on their sportsbook.
Thing is you would need to get approval from your vip host so to do it.
I don't know about that much someone will wager on a single match on the site, but if you wanted to wager $1000 on a market you should be able to if you want and not be limited just because you won on those bets previously.
Very sad if they can not allow their players to wager what they want.