I'm running into this bug as well. Here's the little bit of information I have so far, I will post more as I see more:
-I am playing in sandbox mode
-I was able to compete in a Tournament in Dubh Linn early on, betting the max on myself everytime. I eventually won this tournament with no issues.
-The second tournament I competed in was at Cruaghan. I was not able to get past the first round of this one.
-After defeating all enemies in round 1, the game never advances to the tournament screen. As if there is no "win condition".
-I checked the map for enemies still left, there are none. Troops will still respond to commands, but will stand still if told to "Charge".
-I reloaded the game several times, restarted my computer, and tried not betting on myself (as well as other bet amounts) and none of this helped.
That's all I got so far. I'm gonna mess with it some more and see what else I can find out.