So now I'm getting a better picture of this reading THR and other reporters on twitter.
They bumped heads on tone and they didn't like lord and miller bringing an improv style and letting the actors go off script, which is what they've always done so it's weird Kathleen and crew didn't think of that before they hired them.
Apparently they tried to make han a more comedic character and lucasfilm-rightly in my eyes- balked at that.
But the ultimate fatality was Kathleen wanting to pull a rogue one and bring in another creative to oversee the reshoots. Unlike Garreth on rogue one, those two cats weren't having it lol and they said "fukk that" and they got their pink slips