Tried cheesing it with a friend, didn't work. She got it on our 2nd run despite us doing the exact same, so we tried with me afk-ing the entire fight, then me afking until the last part where u get 10min buff and there are only white guys anyway, then tried me joining for the split phase. Nothing worked, got it done solo eventually.
Also: You get a buff/debuff as soon as you make a "wrong hit" that stacks up to 10 and says it will knock u back when you reach 10 stacks. So you can pay attention to that to check if you are still eligible or if you can already restart.