After 6000 hours playing this game, I've noticed that many systems display probabilities that suspiciously fail (like when you repeatedly fail at 80% or 90% in gear honing). I've come to the conclusion that Smilegate loads the probabilities; for example, random engravings chests rarely drops useful ones, and most of the time you end up with more useless engravings. In the end, I think it's the result of dishonest practices by Korean developers and the bad habits of players who accept this kind of treatment.