Article versioning does not properly deal with versions across tabs.
Steps to reproduce:
Install example client
Turn on simple article versioning (Administration / System / System configuration)
Go to SEO-tab of article "Just Publish"
Set page title to "Just Publish today" and save
Go to editor tab
Set headline 1 to "Just Publish 1" and save
Set headline 1 to "Just Publish 1 2" and save
Set Article versioning to advanced
Go to editor tab of article "Just Publish"
Go to SEO tab
Page title for draft version is empty (instead of being "Just Publish today")