Zombies Split into Multiple Zombies

Zombies sometimes suddenly have a second zombie right next to them. And no, this can't possibly be an intended feature, because nobody would ever think this is a good idea. Zombies aren't planarians.

There's adding additional challenge (which can be done with improved AI, aggression, group tactics, etc)... and then, there is stupid. Or a glitch. Which is what this simply HAS to be.

Please fix it soon. It's absolutely ruining hardcore games with unfair deaths, due to fighting one zombie causing another to appear within my hitbox and killing me almost instantly and unavoidably.