file permissions update wordpress, themes and plugins

hopefully someone can help me

I can recently, no reason, no longer do an automatic update of plugins or themes. I get the message that WordPress can not create directory or that the file permissions are incorrect.

I put the cash folder to 777 and also the themes folder and plugin folder. but without result. I have removed the upgrade folder and recreated with rights 777. I also downloaded a clean version of wordpress and replace everything in my root except the content folder, wp-config and .htaccess file.

I can manually via ftp to perform an update, but that's not really very convenient.

Does anyone have an idea what the problem might be?