I've noticed that in many battles some units will not be deleted when they die. The tile is still occupiable by other units, so when they do occupy the tile with the dead unit it looks like two units are in the same tile. Also the dead unit still appears as alive on the troop banner in the upper left, and you can still select the dead unit and tell it to attack, but it will not do so, just saying 'you cannot do that right now'. Finally this accompanies other battle animations being skipped, or attack animations getting stuck in the charging phase, and never resolving the attack animation. I have one mod, super culture pack, but it occurred in both modded and non-modded games. 

Thanks folks.

Sam