Can't move a page to its correct place in the hierarchy.

When I try to move a page into a different location in the hierarchy, the page appears to move to the correct location, but it then moves back to where it was previously (at the bottom of the list in its parent page).

The page is located here: https://confluence.atlassian.com/display/TEAMCAL/Team+Calendars+5.0+Release+Notes

I have the correct permissions for the page/space, and I'm able to move other pages in the space and under the same parent page.