I'm with the others - the most usual cause of scratching is contamination and that can occur from an external source (Swarf, failing to clean the stone from the previous lap, contamination on the polishing lap, or a build up of too much excess polish combined with a 'heavy hand').
Suggest a final cut at 1200, a pre-polish at 8000 and a final polish at 50,000 or 100,000 - not charging your polishing laps with too much material(making sure it is reasonably evenly spread on the lap) and ensuring you clean your hands then clean the stone at each sequence. Work at lowest speed when polishing.
Best of luck.