Replaced site URL in GMB and rankings decreased significantly

We are in the middle of a rebrand and switched the domain (site content is still the same for now). All pages were 301 redirected and submitted the domain change via Google Search Console last week. 

Today we updated our GMB site to the new url and immediately saw our placement in the map box of the SERP go down by ~8 positions. 

Is this temporary while GMB does a review of the new site? Is there a way to recover our ranking faster somehow?

Any tips appreciated 🙂