How can you remove the edit lock on a node? When I try to save a node I am working on I get this error message.


  The content on this page has either been modified by another user, or you have already submitted modifications using this form. As a result, your changes cannot be saved.


What is causing that issue and how can I remove the lock?
Did you use the back button to get to your edit page? Have you tried manually going to the node and clicking the edit tab again to see if it reoccurs?

This message is caused when either (1) two users access the edit page and one user saves changes before the other user gets a chance or (2) when a user edits content, saves it, and clicks the back button to get back to the edit page.

https://obrienmedia.co.uk/kb/drupal-website-management/avoiding-the-the-content-on-this-page-has-either-been-modified-by

Are there other users signed in? When all else fails (or rather the first step of troubleshooting always) Flush all cache. Clear your browser cache. Close your browser out. Re-open your browser. Attempt to recreate problem. Is it still happening?