Forum:The Best Defence Glitch?

I'm having problems with this quest. I have gone to the base and destroyed three towers, but the quest hasn't finished. In fact, I've destroyed all the towers in Sarin's base after destroying three did nothing, but the quest still says 0/3.

Have I missed something or is this a genuine glitch in my game? I can tell it's not common cos no one else has mentioned it...

Thayan