The scenario is too sketchy to give a detailed answer. While there are bad apples in every bunch, I would like to think we all would not bring a case that has no merit; indeed we are governed by ethical rules that prohibit it. None of us has a crystal ball as to default or active defense. Default would likely lead to collection efforts, which will wake up the other side and likely lead to removal of the default. So we all assume active defense, as should you. Frivolous or not I suppose is in the eye of the beholder, but bringing a case that you expect to lose would fit that definition in my book.
To questioners from West Virginia & New York: Although I am licensed to practice in your state, I practice on a day-to-day basis in Massachusetts. I answer questions in your state in areas of the law in which I practice, and in which I feel comfortable trying to offer you assistance based on my knowledge of specific statutes in your state and/or general principles applicable in all states. It is always best, however, to work with attorneys and court personnel in your own area to deal with specific problems and factual situations.
Rule 3.1 of the Massachusetts Rules of Professional Conduct, which governs the conduct of Massachusetts attorneys, prohibits a lawyers from filing frivolous claims that have no good faith basis.