Noticed in that wpbeginner link the first few user comments refer to posting in tabs which have remained “logged in” when logging out has occurred on another tab. Has that happened to you at all?
Also, just as a general rule of security here, I de-activated wp-phpmyadmin as it has vulnerabilities when not used. Posted for clarification here.
Happened again today after successfully submitting a post to another thread, so no logout issues. This time, hitting the back button revealed no post content. Must have been too quick for AutoSave, (or something) – changed the interval to 45 seconds.
Edit: Most likely related to an oops in the Cache Enabler Settings. Cached pages now expire 10 hours after being created, before they never expired, so could have been sending expired nonce data to the WordPress engine. The site cache was also cleared when a new post was submitted, now turned off. Cache is now turned on for mobile devices. 🙂
The wiping of the post cache isn’t supposed to happen at all when clicking the back button. Didn’t happen prior to June IIRC, so something must have happened to trigger the error handling in Cache Enabler- might have to query them.
Post content is also wiped when this error crops up (also see private sandbox thread):
This page can’t be displayed – your request has been denied for security reasons.
The incident ID is: XXXXXXXXXXXXXXXX