I have yet to shoot a friendly and not have KS work. While I'm not saying it's impossible, I find it highly unlikely. I hit the wingtip of another friendly plane with a single 75mm, and it took the entire left wing off of my plane.
Happen to have film, or can you recreate it? I suppose you could have had some lag or some other weirdness that delayed the damage, but even that should catch up with you.