Hi La Unión | Atazar
first on the video we see that you are not really at 90 degree compared to the lock.
Second, the missile activates its own radar at a certain distance from you that's why you have the lock missile 9 seconds before impact
Thirth, is better with Tacview, we have more informations
https://www.youtube.com/watch?v=Z-2sWS_Rom4