? More info?

I think he's talking about the one that died?

if you have -50% attack  and the guy you hit has +50% and maybe some military research i could explain it

Droids refusing to take planets despite your orders and their superior numbers, shortly after one of its comrades malfunctions...

It seems as if your empire is experiencing the first signs of the robot uprising.  However, this is a good sign.  If this was an amoral robot uprising, the AIs would have had no problem conquering the planet, then simply overthrowing you so they had a greater power base upon which to secure their control.  Instead, your AIs refused to commit the massive genocide you ordered them to commit by not taking the planet.  This likely means that you developed a moral AI, which means they aren't necessarily out for blood.

I'd suggest you begin treating your droids kinder, giving them better benefits and possibly reducing their work hours in the hopes that they may realize that they can, in fact, live peacefully with your species without the violent civil war.  It seems they have qualms with committing mass genocide over large planets, so that might be a good concession to begin.

Hope this helps!