Edited page not saving correctly.

I have a new page that’s failing to save a change to the Sidebar Settings correctly. In particular, I want to change the Sidebar Settings option “Select the desired Page layout” to “No Sidebar”. I change the selected option then click Update and it reverts back to “Default Layout – Set in Enfold Child > Sidebar” when the page is reloaded. I’ve disabled all plugins and updated the theme to the latest version (4.0.5) and tried switching from the child theme to the parent, and none of those things have helped.

I created another copy of the page with identical content and settings, and that page is working, but we can’t just rebuilding pages on the site every time we need to edit something. I had a similar issue last week that I worked around (https://kriesi.at/support/topic/fullwidth-easy-slider-disappears-from-page/ ) but in that case elements were disappearing from the page after an edit.

Are you able to please advise on why the sidebar setting isn’t saving? I’ve provided login details and a link to a test copy of the site.