When you edit a stable version of page with unreviewed changes (Flagged Revisions), it always overrides with those unreviewed changes, even if it's not needed. I think, if the user with an editor/reviewer rights edits the stable version, the mechanism should save his edits with this version, excluding the rest. The problem is that now if the user with those rights edits the stable version (even as a minor edit) then it saves automatically with all unreviewed changes marked as revieved, which is a big bug.
Eg. user is viewing old version (stable) of the page, but the edit links are pointing to the latest version. Normally when you are looking the old version of the page then edit links are pointing to that version and there is warning that you are gonna to edit the old version.
Steps to replicate:
1.) Go to page with pending changes
2.) Select the stable version of the page via "Read" -tab
3.) Click the edit button