It is not a bug, he broke the terms and conditions which i stated at the top of my posts and it is written black and white in our T&C.
I'm sorry but here you said it is a bug.
You used a bug in the slots that is not reseting the bonus status, you finished your money and deposited to return to the bonus status. which is illegal, since once again, you can not profit from the bonus money we gave if you not reach our conditions.
Now you are saying it is not a bug?
I don't think it matters that he played to near the bonus rounds using bonus funds. There was nothing in place to stop him and your terms didn't say anything about these games not being allowed. I think this strategy is why some games are blocked when you have a bonus on softswiss sites and fortune jack. You didn't block these games until after the player won so there is no excuse for you to not pay out. I would understand if it was a large amount but you said yourself it is just pocket money.