Depends on how unique was the time at which it was intended to execute. Was there some event, spark in volatility, etc? If no, and if it starts to happen often you have to simply change your broker, because evidently execution sucks.
I think orders are executed when the price hits it but in few cases chances are that the price does retraced back from our desired level. So we can pick a little earlier price point just to ensure we can ride the right trade and earn money from it.
