Case is - after using Yamato skill "Fliyng strike" and then immediately! press "Crimson slash" skill, then it will be played some fake animation with sound, but "Crimson slash" wont works and wont be on cooldown, it just spent a few second. If you perform action, like shooting or melee attack, immediately after "Flying strike" and use after that "Crimson slash" - then it will works well
Video where the problem is shown
Video where the problem is shown