Edit a content in v1
By a search grid aside, change the title of the content. Content is now v2.

You cannot save the content at this time because you started edition at v1 and it is v2 now.

Wait for the autobackup : it will store your v1 data, but the server will memorize it as v2 data (the current version)

Refresh the browser
Go back in edition and accept restoring the autobackup
Now you can save your v1 data to overwrite current v2 with no warning