As of a few weeks ago, I can no longer change anything inside 'Software & Updates'. If I click on checkboxes, select different items from a dropdown, or edit/add/remove PPAs, the fields just stay as they were. (Clicking on a checked checkbox leaves it checked.) I can still add PPAs through terminal, and they do appear in the 'Other Software' tab in 'Software & Updates'. Can someone help me troubleshoot?