Is a union required to investigate every grievance before taking it to arbitration?

As this court stated in Ayangma v. PEITF, 2014 PECA 9, at para.23: However, the employee is not entitled to the most thorough investigation possible. An employee does not have an absolute right to have his grievances filed or taken to arbitration. The union has the exclusive right to determine whether to file a grievance and whether to take that grievance to arbitration. A union thus has considerable discretion as to the type and extent of the efforts it will undertake in a specific case. This discretion must be exercised in good faith, objectively, and honestly after a thorough study of the grievance and the case. ... It follows that, subject to compliance with the parameters of the legal duty of representation, a union is not required to take a grievance to arbitration if it does not believe the grievance has merit.