"Inactivity Timeout" Message when Saving Page

When attempting to save changes to individual pages in Omeka S, the page just displays an “inactivity timeout” message regardless of changes made or time since login. Exiting the site and logging back in results in some changes being restored, but not others (as does backpaging from the error message). I am new to using Omeka and unsure if this is just user error, but I cannot add things to pages due to this error disrupting every attempted save.