From my experience, these exchanges sound right on target.
There is always humor and horseplay on the set of a movie. Things go wrong. The special effects don't work. There are mistakes, and sometimes the mistakes are amusing. Cell phones do go off in the middle of tense scenes. People do blow their lines--you have no idea how hard it is to remember all those lines!--and that can be treated with anger or with humor; it's much better to handle it with humor.
There is a lot of stress and pressure on the set of a movie, and people relieve it by making jokes or dissolving into giggles that are provoked by tension. Very often the jokes are coarse if not obscene, for movie people as a group are not highly educated, beautifully mannered, or reverent. The fact that these exchanges were all so clean and mild indicates to me that they were real, but were tempered by the actors' knowledge that they were working on a project that was holy in its way.
In making a movie like this one, in particular, it is going to be impossible for everyone to maintain an attitude of agony and misery all the time or they'd go insane.
I agree. I found them very realistic as well. Too realistic and mild for them to have been made up by someone trying to cause trouble.
IOW, if they were made up outtakes, they would have been much worse.