New content inserted at top of page after a simple edit, and redundant layout sections cannot be removed

I have a Confluence page for a project that I am working on, and yesterday afternoon just before I left, I added a link to a child page in one of the page layout sections. Doing this appears to have caused the entire content of the page to be inserted at the top of the page, while leaving the previous content below - and slightly breaking it too (see the link in the third column of the 3-column section).

Furthermore, I am unable to fix the page by removing the redundant sections. I can remove 2 of the 3 redundant sections successfully, but whenever I try and remove the third section - no matter which order I remove them in - all content is wiped from the editor window, including the non-redundant sections.

I have copied the page, and the copy also experiences the same issue.

Original page: https://extranet.atlassian.com/display/D/Project+Red+Pill
Copy: https://extranet.atlassian.com/display/D/Copy+of+Project+Red+Pill

I've attached a couple of screenshots, but I'm also conveniently located on level 2 next to Benjamin Crothers - if you want any further information or a demo, feel free to come have a chat!