Settlements can be defended by any player, not just Balur.   The defenders you encountered were not Balur's troops.  They were defense sent there by player(s) as a trap to catch those who fail to send scouts first.

I used to join with allies and league mates to set up a wall of tears at sapphire settlements back when they still existed.  I really miss those days.

Hello! The reported case cannot be classified as a bug since this is a part of the regular gameplay. I have moved your topic to Game Discussion thread.

LoL.