“Spinning wheel on modify page, ajax call”

I was just about to post to this… Im not sure who to inform, Wordfence or you guys but Ill confirm what @babayard is saying.
If Wordfences new firewall is enabled you cannot modify any pages because the admin-ajax.php is flagged error 403 when checking the console.

I had not tried the “learning mode” then switching to Firewall-enabled again. But I can confirm disabling it resolves this problem.

Good luck guys :)