Basically if two melee heroes are pushing a tower and all the creeps die, they'll end up in a rather unfortunate loop. Let's say we have Hero A and Hero B (both bots).

Tower targets Hero A after it kills the last creep. Hero A runs back out of tower range, but Hero B keeps wailing on the tower. The tower then switches to Hero B who begins to run away... but Hero A sees that the tower is focused on someone else and moves back in to swing at the tower. Then as Hero B gets out of range, the tower focuses on Hero A, who begins to run as Hero B returns back toward the tower.

This lasted until more creeps came and distracted the tower. I think a subtle logic change needs to be made somewhere.