Hi,
Yes, contacting these agencies will help you find out the status of your immigration security screening and also, you would be able to figure out where exactly your file is stuck. At this stage, all IRCC / local visa offices will tell you is that your background checks are in progress and they can't do anything about your file unless this step is completed.
For me, it has been more than 16 months. Everything is passed/met as per GCMS notes. Security is blank, and IRCC says my background checks are still in progress. It took less than a month for CSIS to deal with my immigration security screening, and it's been almost a year since CSIS was done with my case.
Next, CBSA - I am awaiting a response.
Have you requested GCMS notes? What does your local visa office say is the reason for the delay?
If answer is the same, i.e., the background checks, then delay is probably from one of the security agencies (CSIS, RCMP, CBSA).