Yasuo Yomuu's bug

Just got second against a guy that was running assassins with a yomuu's 2-star Yasuo. No matter how far away he was from my units, his Yasuo just wouldn't jump like an assassin. He always just ran forward with a massive shield and drew aggro of my units. It was absurd. My units walk forward against his full assassin comp because of the Yas, and his yomuu's and BT with shield literally sustained him while his actuall assassins destroyed my team from the back forward. Impossible to position against and extremely busted exploit. Assassins with a free frontline.