Obsidian Arrow for Mayas don't work?

Yesterday i had a game as the Mayas and researched the Obsidianarrows.

I was wrecking the enemy base but was confused how long it took!

So i tested how much damage on arbalest do to a building!

And it was only 1 damage???

Tried it today again against KI and the result was the same!

Please report it in bug section!!