defines.command.attack_area completes prematurely?

[heyqule]

My mod uses defines.command.attack_area command. I noticed that the attack command seems finish prematurely. Like the biters attack a few time and the task is marked as finished. Majority of the buildings in the area are still standing.

Here is how it looks in action.
https://www.youtube.com/watch?v=zt4UEdYBiBE

Is this by design? or is it a bug?

If it's a bug, I can provide replication details in a bug ticket.