IMO this might be the most significant point in the doc. "Ship’s XO Sean Kearns refuses Captain’s mast, is court-martialed."
While underway, commander/captain is judge, jury and executioner for disciplinary issues. They call it "Captain's mast" and the powers that come with it are wide and can be extreme, including demotions and docking pay.
The XO refused to receive the ship commander's punishment while on mission. Tantamount to a mutiny.