There is always the option to return to the pervious state before updates. Here is one way to do that…
Just set up the script, it will shjow you a calendar for choosing the date to return to, and return all packages to the state of that day. Do not re-upgrade until you hear what happened, and that it is fixed!
Or - better yet, try to figure out from the list of ‘pending updates’ (try checkupdatesext in the terminal for a list) what it might have been, then add it to the pacman ignore list, and have the rest of the updates as normal.
Edit: - There is a post here that suggests it might be cinnamon-settings-daemon that causes the problem… perhaps you could try to downgrade just the one package if so. (terminal downgrade and package name)