My girlfriend just completed the final faction quest with Scoiatael (win 5 games) but instead of getting the reward the win counter just resetted to 0/5. We already restarted the game once, but that didn't help.
The last, after the fifth is an endless quest.
Whenever you fullfill it you get 1 faction point in the challenge, but no rewards like reward points.
The quest then resets itself so you can keep pushing your own faction.
The only quests with rewards are the 5 initial.
(Win 5 is the endless quest afterwards, there are no personal rewards for it).