Question about Mythic mannoroth.

[Vestig3]

So ive been progressing on Mythic mannoroth and we are pretty close to the kill but what bugs me is that somehow i cant charge the boss when he does the push back from massive blast so i did some reading and its coz he stuns me but somehow if i watch video's from warrior pov's or Sco on his twitch he manages to charge the boss and i realy wanna know how its done just for the sake of knowledge.

[KaPe]

Are you looking at the same phase? He only stuns during the final 35%, normal pushback doesn't do it. Or maybe it's some stun-break that works.