Unfortunately I did not make screenshots while troubleshooting this, so I do not have the exact outputs.
Each time I opened up Software Center over the last couple of weeks there were several GNOME Application packages shown with a status Installing in the Updates tab that never completed. It turned out that these were all flatpak packages, so to troubleshoot the issue I executed the following command:
$ flatpak update
This command raised an error that a GNOME runtime was no longer supported, and that the installed flatpak Kooha was using this runtime. I uninstalled Kooha using Software Center, the flatpak update command no longer raised an error, executed the command:
$ killall gnome-sofware
restarted Software Center and the Updates tab no longer showed these packages with status installing.