I get them routinely It is now 2021 and apparently continues after three years!
I had this issue too. I sat down at the computer to update two Garmin GPS units. The first update went well. The second update brought the spinning wheel. I tried quitting and restarting Garmin Express to no avail. Then I restarted the computer. Also no joy. I resolved the problem by quitting the application under the file menu (File -> Quit) and then quitting the menu bar widget. Then I reopened Garmin Express by double-clicking on the app in the Finder. Then it worked.