What are the settings that you use (noise, blur, face refinement)?
I use GP a lot and I have found that the main problem in frame by frame processed videos is with the stars : they are “split” (GigaPixel redraws two sharpened stars instead of one blurred) and they move from frame to frame.
It seems to me that you also have this problem in your video. Did you achieve to reduce or solve it?
tbh i didnt even notice that issue and i forget the settings i used in gigapixel.