I was in the same boat and was told by the frustrated official who interviewed me that the mistakes are being made by new employees.
My sister and I applied for our citizenships at the same time and hers was processed within 3 months, granted that she has been a PR for 30 years and I, only 2.5 years. I was asked to submit colour photocopy pages of my 2 passports which I promptly did. Two days later, I received an email that my test results were suspect and I had to re-do it. Then, they scheduled an interview for me.
During the interview, they informed me that a new employee had mistakenly emailed a couple of people (including me) to re-do their tests because of suspicious activity. I had spent the last 4 days studying for the test and so I was pretty pissed (but laughed it off because I wanted my application processed asap). I was then informed that I had not indicated my day visit to the Bellingham, USA. Apparently, they have info on when we leave the country but not when we come back. They assumed that I was not being truthful about the days I was out of the country. After it was all sorted, the very professional and competent interviewer said he would approve my citizenship. He apologised for the delay and inconvenience. I received my citizenship 3 days later.
Hope this eases your anxiety. It's likely an issue on their end which can be easily resolved with an interview. I hope they reschedule it asap. Best of luck.