Prop firm disavventure what you think about?

[pippoio]

Hello, i had a disavventure with mff. In the market opening, in a moment of high volatility thei challange broker refused some operation with the error "closing at 0.000 off quotes" and when the daily dd reached -5% the problem is solved and the position was closed making me lose the challange. They say that this is a normal slippage but a 5% of slippage i think it's too much what you think about?