@Katharsas It appears that it does not matter who causes the projectile. We tested this by sending my commander with hold fire to LFBJ_0911's commander. His commander rotated to aim, then my game lost connection with him as soon as a shot should be fired. (The firing animation did not play yet.)
Can it have something to do with communicating new projectiles?

I have played FAF with LFBJ_0911 and have tried to find ways to trigger the anti-virus response mentioned above. I have set a group of tanks to attack the ground and upon firing their first shot LFBJ_0911's game gets stopped by his anti-virus.