How often does the base map update? I see that it’s not at the same time as a city sync.
Mapbox handles the base layer (the base visual, greenery/waterways/streets/etc, for anyone unfamiliar) on their own schedule. 
I have no idea what their cadence is.
I handle the node/street/city border stuff. The system tries to sync batches of cities every minute, skipping minutes when there is a queue of post-processing. The Status page (linked from the bottom of every page) shows that wait time.
Supporters can bump cities up in the sync queue from the menu on the city page.