Cannot update 3.5 post after upgrading to 3.6

Have you tried:

– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).

– switching to the default theme to rule out any theme-specific problems.

– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.

– re-uploading all files & folders – except the wp-content folder – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.

Is there no debug mode or whatever? This sounds like did you already reboot your computer of reinstall Windows.

Before the upgrade everything worked fine.

There is no magic bullet in these situations. This is just the start of basic troubleshooting and is a process of elimination deliberately designed to locate the root cause as quickly as possible by first removing the most obvious and common culprits via a series of (often) temporary steps.

Do you want to locate and, hopefully, fix the problem on your site? If “yes”, then please help us to help you and carry out the changes that we suggest.

I deactivated all plugins and changed the theme to default. No difference, sometimes it did a real 404 instead of the “proper” message: Oops! That page cannot be found.

Now I replaced the files in the root and WP-includes and WP-admin with freshly downloaded files. Also renamed the wp-plugins but there is no difference.

Site url?

https://blog.compower.org

but the problems only resides when editing an older post.

I do get a suspicious line in the access.log:
xxx.xxx.xxx.xxx – – [06/Aug/2013:16:39:24 +0200] “POST /wp-admin/post.php HTTP/1.1” 403 42254 “https://blog.compower.org/wp-admin/post.php?post=263&action=edit” “Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko” blog.compower.org

Can we see the site using the default Twenty Thirteen theme with all other plugins deactivated?

I do get a suspicious line in the access.log

That’s just you editing a post.

I understand but why the 403 respons? https://en.wikipedia.org/wiki/HTTP_403

activated the default theme and renamed the plugin folder. Still same result??

No idea. That’s definitely nothing to do with WordPress itself. Have you asked your hosts about it?

activated the default theme and renamed the plugin folder. Still same result??

When did you last repair all of your database tables?

How do I do that? That will answer your question ;-).