Set your Basecamp detail from "medium" to "highest" and see the results.
It's not "basemap", it's "overview map" which is a far out zoomed version of the map you see on the main screen.
With detail set to "medium" your "overview map" shows your map at 8 zoom levels higher.
Try this: with detail set to "medium" start at a zoom level that you see both the map and the overview map.
Start pressing the "-" key to zoom out and from the time your overview map disappears, press "-" 7 times more and your map will disappear too!
With detail set to "highest" map and overview map never disappear from the screen.