Ask your parents to fly back to Canada. Otherwise the process is long and costly and lots of headaches. Two plane tickets can solve everything. Good luck!
It means CIC will ask more document. If it shows: reviewing additional document, then it's ok. Mine has been like this even we have already landed. When it shows N/A like some of my friends did, they all were requested something again.
From the previous year experience, going Ottawa would be faster in the end. Your father probably doesn't need PCC from Canada, only Chinese one is sufficient. But you need to wait and see, CIC will give the detailed instructions. Good luck!
My time line:
04-May-2017 : Application Received in Mississauga
07-Jun-2017 : NO AOR Received, but it shows in ECAS.
14-Jun-2017 : Sponsor's Approval (Local Visa Office: Ottawa)
04-May-2018 : Medical Request Received
08-May-2018 : Medical Exam Done
10-May-2018 : Medical Passed & Background...