Sounds to me that the way you upgraded was not valid and has resulted in A Mess™.
Some options would be:
You did an image before starting the upgrade. You restore that image and try again with the upgrade.
You haul off all your personal content and reinstall from scratch and then restore your personal content. (This is a hassle because you would also have to reinstall any additional packages that you previously had installed and you would also have to re-establish any particular settings changes that you had made.)
If nothing else, can you do a Live Boot of 10.3 and confirm that gnome-control-center works fine when booted thus?