The "Battle Master" quest ends with the subquest "Lots of Weapons," which gives target production numbers for six types of weapon.
I've succeeded in meeting the target (by blowing guild coins on zombies), and while all six types are highlighted in green and checked off, the button to complete the subquest and claim the prize won't appear. The subquest title in the listing of quests also hasn't gone green, nor has the "Quest completed" bouncing flag appeared.
I've logged off properly, restarted my computer, etc.
2K guild coins down the drain! Useless buildings built! Well, these things will happen.