It can be reproduced on clean install of 4.4.5.

• Create new-article page under demo-project/about/subsection-articles using Article template and activate (first version)
• Go to author's /demo-project/about/subsection-articles/new-article.html web-page and edit Article Header abstract, then activate it (second version)
• Go to author's /demo-project/about/subsection-articles/new-article.html web-page and add new content - activate it (third version)

There is no problem if you try to compare current version with previous, but when you try to compare second version with previous or current it:

• displays as new content even areas that didn't change (see attached screenshot)
• creates new content node extras in JCR:/demo-project/about/subsection-articles/new-article
• throws error you can see in attached error_log.txt file