In order to better support collaboration and prevent accidental overrides, we have implemented a lock system for quest editing.
When entering a quest by clicking on the quest title in Content page, you are defaulted to view-only mode, where no changes can be made.
If nobody is editing the quest, you would be able to make changes once you click on the "Edit" button (top-right). If someone else is editing the quest, you would be notified and given the choice of taking over the editing access.
If your editing access is taken over, you would be notified the next time a save or auto-save happens.