Ways to reproduce this:
1. Create a new unprivileged (non-admin) user
2. Log in as admin, create a new page and give edit rights to the unprivileged user
3. In Safari
3.1 Log in as the unprivileged user and access the page
3.2 Modify the page and hit "Save & View" or "Save & Continue"
Result: All your modifications are lost and you see the previous version of the document.