When trying to edit a page template (or any other PHP file) using Appearance > Editor, I am getting a “Scrape nonce check failed. Please try again.” error. It started happening in WordPress 4.9.
I am using GeneratePress 2.0. I have contacted the host, and they tried changing PHP versions, but still got the same error. I have deactivated ALL plugins -> the error persists. I have deactivated the child theme, as well as changed to an entirely different theme -> error still persists.