I made an example that seems to work.
https://drive.google.com/file/d/0B5FlDY ... sp=sharing
But I had trouble that an enemy stuck on another enemy after some amount of time. The same effect did I had with the solid behavior.
So the enemies now hold a distance from 2 pixels if they collide. Fewer and they will stuck. It is possible that if your game get choppy they will stuck on each other again. Then you have increase the distance.