Because of the way Oxygen saves global styles, classes, and settings, multi-user or multi-tab editing with Oxygen is highly discouraged.
We recommend using a single tab when working with Oxygen to avoid issues where one tab is saving older data than another, resulting in overwriting your new changes. The same scenario can occur when two or more users are working in Oxygen at the same time.
To make it easier for teams to collaborate and to prevent this type of issue, Oxygen has built-in automatic Edit Locking.
When Oxygen is open, the following will occur:
The "Edit with Oxygen" button will be replaced with a warning that Oxygen is already open. This change occurs globally across all posts.
The WordPress "Update" button on the specific post being edited with Oxygen will be disabled.
Note: When the edit lock warning is shown, there is an option to open the builder anyway. This should only be done if you are very confident that you understand the consequences of working with Oxygen in multiple locations, or if you believe the edit locking should not be active.
When Oxygen is locked, it is safe to edit the WordPress or ACF content of posts not currently being edited in Oxygen.