A NixMash Blog update has been pushed to GitHub with the fix for Post Content not being saved properly in post backups. The fix is described in this post.
If you're like me you compose your post in a nice Linux WYSIWYG Desktop Editor, copy the source to your CKEditor, save it, read it in another browser tab, save it, re-read the updated version, then after about 10 save and review cycles you finally publish it. That process requires that the Post is updated when saved for review in another browser tab refresh.
When the post wasn't being updated I assumed it was a caching issue on the server side, so that wasted some time until I realized the only field not being updated was the Post Content, or more specifically, the CKEditor textarea content.