It's caused by failure to follow directions.
Check out the torque spec that's engraved on the lockring. 40 nm = 30 lb/ft. That's a good amount. Imagine a 30 lb weight hanging off the end of a foot long wrench. It's certainly more than I would use if I were depending on my own judgement. If you tighten your cassette that amount, it will lock all of the cogs together so that individual cogs can't bite into the freehub body.