I think the issue has been there for a while. It is probably due to a bug in recent versions of gnome-setting-daemon, which clears data in clipboard when the app is closed. Thus, when the command gnome-screenshot -a -c runs and finishes, the screenshot is saved to clipboard and then cleared. That is the best guess for now.
For more information and updates, please refer tohttps://gitlab.gnome.org/GNOME/gnome-screenshot/-/issues/66