A common occurance in this build is that during missions you are kicked back to world map and have to start the mission over again. Very annoying when it happens several times while you're tracking down, or already cornered the last alien.
It's possibly related to having retried the mission.
It may also affect relations with nations favorably, as it didn't take me very long to get them to exuberant with a bunch of this happening. My guess is every kill I made counted, even if the mission flickered.