I'm no programmer, but from what I can see, everytime you pick up a thrown enemy after you threw them, it counts as another kill, and once you grabbed them as many times as there are enemies in a level, you get the glitched screen since the game counts it as you having enough kills to pass the level but there are still enemies alive so it fails you at the same time.
Noticed that when trying to throw the same person multiple times. Since when there are 2 enemies in a level you have to grab the person, throw tehm, re-grab them and then you get the glitched screen. While when you have 4 enemies for example, you need to regrab them 3 times, or grab one and regrab them once, and grab and regrab a second enemies. Either way, one regrab equals one enemy in the level.