C28. Something in my dashboard is not working (outside of theme settings)

Plugins and (active) themes can interfere with everything in the dashboard as well as site functionality, including each other.

Recently themes are better checked when approved (or updated)​​​​​​ but there are plugins that wreak havoc in a dashboard and yet they are in the repository. One can assume they got there before better checking rules were implemented. However even now plugins have a lot more freedom to add functionality, but also break existing functionality.

​​Whenever having issues in a dashboard, try to get WordPress down to the cleanest version (by deactivating everything you can), and then slowly build your way back to the desired functionality, checking for the reappearance of the issue(s) after every extension activation.