I ran into a weird one yesterday, with a new team.
I had Mirror Master Complete Quest (No Reward Choice) checked and Mirror Master Complete Quest (WITH Reward Choice) unchecked

Yet all the slaves just selected the reward.

Checked it agai,n pushed it out again... no joy

So then I checked Mirror Master Complete Quest (WITH Reward Choice) pushed it out
then unchecked it and pushed it out

And it worked as expected, the slaves stopped mirroring the master if there was a reward.

Weird I tells ya.

Also some feedback, Questhelper with Mirror Master Quest Watch seemed to create a fair ammount of spam. Not really an issue since I use quest helper to watch the quests I just disabled the quest watch option.