Issue after page edit

Hi there, I’m hoping you can help with a strange issue I’ve had after trying to edit my homepage. I’ve used Enfold for a few sites now and haven’t come across this issue. Basically, when I tried to edit my homepage I got the following error:

Method Not Implemented

POST to /wordpress/wp-admin/post.php not supported.

Then I went back to edit the page again and, as has since been the case, the Publish widget on the right loads, as does the page title field; then I just have the Default Editor button. Clicking the Default Editor does nothing (no JS errors in console). I can see from inspecting the DOM that #postdivrich_wrap.avia-hidden-editor #postdivrich is set to display: none. Within .wp-editor-area the text color is set to white, which if I change I can then see all the page content (as shortcodes). On the front end of the site, the homepage is fine. I tried creating another version of the page but still had the same issue after trying to edit it. This hasn’t happened to any other pages, which is baffling!

What may help identify the issue is the following warning in console, and this doesn’t happen for other pages when in edit mode:
event.returnValue is deprecated. Please use the standard event.preventDefault() instead. load-scripts.php?c=1&load%5B%5D=jquery-core,jquery-migrate,utils,plupload,plupload-html5,plupload-f…:4

Any help on this would be greatly appreciated!