Why have a character repeat a phrase over and over....

Okay, I think what the writer was attempting was a technique called ‘conscious repetition’. Used correctly, and sparingly, this can be a powerful tool that can elicit a variety of emotions throughout the course of a film.

Think of yourself and your sister (or best friend) sharing a totally stupid joke.

 Perhaps it’s something one of you reads to the other from a newspaper. It’s stupid; you both scoff and keep searching the newspaper ads for an apartment to share.  Weirdly, though, both of you remember the joke and the context, and six months later when you’re trolling dating sites online, one of you repeats the stupid joke again and this time you kill yourselves laughing.  It is still stupid, and so inappropriate to what you’re doing that it heightens the humor.

And then time passes, and your sister or best friend is in the hospital dying from a stray bullet fired during a New Year’s party, and you’ll never know who shot her. 

She chooses her final moment to tell you the joke again, and you laugh spontaneously - but inside you’re crying.  As her eyes close and a smile lingers on her face, you cry even harder and hold her close, wishing you were back reading those want ads again together from ten years ago.

This is an example of how conscious repetition can effectively build emotional impact in your story arc.

 I hope this helps.  And I do wish you good luck with your writing.