Noda B'Yehuda on Breaking an Engagement (12 Adar Sheni)

נודע ביהודה מהדורה קמא יורה דעה ס"ט 12 Adar Sheni 5529 (1769)

A couple gets engaged, and then the prospective bride's grandfather leaves religious observance. Is that grounds to allow the groom to disregard his oath to get married, to let him break the engagement?