psophis

I had these same symptoms, but not using NextCloud. The issue ended-up being an update to nginx that enabled some sandboxing features that was fixed by adding the webdav directory to the systemd config under ReadWritePaths. Might be the same issue with NextCloud see: https://wiki.archlinux.org/index.php/Nextcloud#Explicitly_permit_Nextcloud_directories_for_php-fpm