Chiming in here too as I was running same offer as Ivan through PKM.
Basically there was an error on advertiser's end that caused pixel over firing.
Since the pixel was over firing and CR was good I was sending all the traffic I could.
This went on for a week after they noticed the problem.
It was clearly their fault , but they refused to pay.
I got on the phone with with the advertiser and Yousif and their answer , was a "it's our fault , but we are the advertiser and we don't wanna pay for our error" in a nice way.
So long story short , advertiser was being a dick and didn't pay PKM ( actually paid $1800 out of $100k they should have... ).
However Yousif took the hit and covered my advertising costs , so props to him for stepping up.
So PKM is legit on my book.
So.....are you going after the advertiser?