I’ve realized that people are angry about some issues but they vent out on other ones. The real problem with your manager might be that you are getting too close to the boss and the possible promotion in near future. But they vent out on you over some statistical error in the monthly report. If someone is arguing in a heated way then pause and think over the elephant in the room that’s bothering if the relationship is worth saving in the first place. By this, at least you can worry about the right matter.