From my limited experience plucking seems to occur most often if you are overbowed too.......??
I know when I first started shooting or I watch a buddy of mine who is still building those muscles the tendency is there to overpull at release and pull your hand away from your face causing the pluck.

Now that I can hold at anchor much smoother I have far less of these but when I start getting tired and I feel like I'm struggling to consistently hit anchor they will happen more frequently.

A pluck for megenerally winds up dead right of previous arrows by a considerable margin.