Was BG status changed in portal to In Progress from Completed & then again back to completed? It happened so in my case.I received my latest GCMS notes last night.
They did another background/criminal check early March, so now my background check validity is until Mar 2023 - this check was done before expiry of my previous check, and before DM.
My file however is still in Sydney NS office, and my local Mississauga office is still secondary.
I think they are probably not doing actual BG check, just changing status in system; so that system does not ask it again if oath is delayed.