Simultaneous editing and the "Break lock" error
The "Break Lock" warning appears when more than one person are editing a page at the same time. By breaking the lock it will enable you to gain control over the page and edit it. Make sure that your site collaborator isn't actively working on the page when you take control, as breaking a lock affects saving capabilities. If you choose to break a lock, and the other editor saves after you have saved your new changes, their version will overwrite your edits and vice-versa.