Cannot set Profile Homepage

Confluence and Crowd sit on their own instances of Tomcat.
In Confluence, when trying to edit the Account/Profile Preferences, and set the Site Homepage to a different page, it works initially. But after waiting a while, or restarting the service, the changes are lost and the Site Homepage is set back to the Site Default.

Support has more details here: https://support.atlassian.com/browse/CSP-10154