Hi There. We're in the same boat. It's truly frustrating how slow the process is. I've been waiting for 41 months.
I recommend you apply for ATIP (Access to Information and Privacy Program) and pay $5. This will allow you to track your case's progress. The website is:
https://atip-aiprp.tbs-sct.gc.ca/
If you don't have an account, you'll need to create one. You should receive an email with your case details in about a month.
That's what I did, and that's when I found out my case had been stuck with the Canada Border Services Agency (CBSA) for almost two years. I initially thought it was with the Canadian Security Intelligence Service (CSIS), but it wasn't. I emailed the CBSA, and my case was processed quickly.
Unfortunately, my background check has passed, but I'm still waiting for the final decision from Immigration, Refugees and Citizenship Canada (IRCC). That's just how IRCC works; you can only wait and do nothing.