Here is another analysis from my side to calm your nerves a little. Now this is just my analysis based on my understanding of the processing, the Immigration and Refugee Protection Act, analysis of my GCMS notes and the trends available forum.
The Background Check is the last step in the processing for all FSW candidates. For the PNP it starts early in the process, but not for all. The BGC is conducted by external agencies, CSIS, RCMP, INTERPOL etc. So when an application has the BGC in progress you will receive a ghost email and it will be followed by a change in the status on MyCIC. Now CIC cannot predict how long your BGC will take. It can be as little as 2 days to as long as 2 months or more. When you receive another ghost email, this time, MyCIC would be updated but you will see no change. This usually means that the BGC is complete and is awaiting an agent review. If the BGC is all clear, the agent will write a note finalizing the application and you are ready to get you PPR.
In the last 2 weeks, CIC has not issued PPRs or those that have been issued are rare. This could be due to various reasons. One of them could be that could have been too many passports sitting for visas and they wanted to clear it before they get back to sending more PPRs. Or that the workforce has been reassigned to some other project, a family sponsorship or spouse, which are the priorities for newly elected government.
In some cases, like mine, my BGC was in progress. It stayed like this for a month. Then I requested GCMS and the next day I received a ghost email. In my experience, my last two updates have been when I filed GCMS. This happens because when an applicant applies for the GCMS notes, an agent is forced to open your file. If there is an update pending on your file, like the BGC report complete, he will update it since he is in the file.
I hope this helps calm some nerves.