Using sandpaper without experience is strongly discouraged. For start-up problems an ink change to a thinner brand (e.g. Pelikan or Lamy royal blue) often already helps. Slight noises with an M nib can come from "squeak" on certain papers — satin-finished, high-quality paper noticeably reduces this without being significantly more expensive. Genuine scratching often comes from misaligned tines; under a magnifier both halves should sit at the same height, otherwise the nib must be straightened. A gentle break-in, with start-up improving day by day, is normal; a proven trick is to start a new line with a tiny dot.