I am facing some serious issues with out Nextcloud server, which has been running fine until lately.
Some users are not able to delete files via the website. When trying to delete a file/folder an error is displayed and the page refreshed itself after 5 seconds. A user with this issue is prompted twice for the password at login and when you try to access content (i.e. show a picture), you need to reenter the credentials again in a password box. Then the content shows.
This happends with the admnistrator account and some users. Not all of them! Some other users claim that everything works as expected! I can see, that the API functions are working fine, because I can still connect users having the website issue to the desktop app in order to create sharelinks.
I have upgraded to the latest version of Nextcloud but without any difference. All consistency checks are OK. All trashcans are empty and locked items deleted (in the DB).
The worst thing is, that when I browse the Nextcloud website from my iPhone, everything works!? I can rename folders, delete files and rename them. This is so strange…
In the nginx logfiles I can see an error:
8160#8160: *13 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Doctrine\DBAL\DBALException: Failed to connect to the database: An exception occured in driver: SQLSTATE[HY000]  No such file or directory in /var/www/nextcloud/lib/private/DB/Connection.php:64
I have looked in line 64 of the specific file, but can not find anything there.
My Nextcloud logfiles say that:
OC\AppFramework\Middleware\Security\Exceptions\CrossSiteRequestForgeryException: CSRF check failed
But I can not make any sense of this neither…
I run Nextcloud 17.0.2 on Ubuntu 18.04.3 LTS with Nginx 1.14.0 and MariaDB 10.1.43.
Does anyone have any suggestions/ideas how to solve this issue?