Sorry if I wasn't clear in my original post.

When I talked about the progression flag/checkpoint, it is meant to be the phase transition with cutscenes.
I believe in NA it is called the door boss? in each of the 4th floor of raid tier. P4S/P8S/P12S. When you drop the boss HP under a certain percentage, a cutscene will play and the boss hp will reset to 100%, as well as the timer for the duty.

I would think it should be fairly straightforward to implement a "part 1 cleared" flag here, and this would alleviate the PF Fraud if just by a little bit. Right now there is no way to stop someone who is new to P12S, to join a group of people trying to prog Phase 2.

And I dont want to blacklist people unless I can really identify 100% they're doing party fraud.. Bad days, pair mechanics, body checks occurs often in game ><