That article didn't go into much detail, maybe I missed it.
During a video session last year Belichick highlighted Gronk on a play where he was unable to hold the edge and made a comment about resistance bands not helping him on that one. Gronk had stopped doing squat and "normal" lifting that the team trainers instruct the players to do.
From all the local stuff, even from some of the biggest homers ( Tom Curran) a rift does exist and the players and coach have no interest in closing it. My guess is Kraft steps in and gets them to play nice for one last run.