Alp, I think you provided typical example thanks.
it is not at the exact cross from the chart that you will know it has crossed live trading but at the close when the new value is calcualted and a line is drawn in between the new point and the last point.
So from there you can see that it can change as much as 50-70 pips from your back test.

Saying that, you could have a look at a smaller time frame (5 Min) when the 2 lines are geting dangerously close and going totally oposite direction at the last 1H close.

S.