Why does this keep happening with aim7's?

The MiG didn’t have this nose pointed at you when you fired. Here’s the moment of launch:

And if you fly the camera down your radar beam you can see the MiG is not actually that far off perpendicular to you. Certainly not head on to you.

The missile stays in SRC mode for the entire flight meaning it never acquired the target, probably because the target was essentially notching at the moment of launch.

Maybe what happened in my client was slightly different from what the server decided to happen. I remember to specifically wait for the target to get out of the notch before firing the 1st missile.

I had different weird stuff happen and the replay results were different from what really happened in my game/client.