Right. See some back ground checking. You know what some times due to bad luck some one's name matches with some wanted people and they get stuck. I think your case could be the same. But its good that you wrote to MP and kept pushing it. Keep pushing it , hopefully you will get it soon. Good luckI spoke to MP office two times and wrote a letter to immigration minister also got back replied from minister on 6th May 2017 as below.
Departmental records confirm that your background checks are pending a review by one of our partner agencies. As a result, citizenship officers in Mississauga have not been able to assess your case as quickly as they originally intended.