Nextcloud usage quota

Continue of discussion of Nextcloud usage quota for user seems not correspond to the folder size on linux:

Nextcloud version (eg, 12.0.2): seen from 12.0.5 to 13.0.1. Using now latest
Operating system and version (eg, Ubuntu 17.04): Raspbian jessy
Apache or nginx version (eg, Apache 2.4.25):

apache2 -v
Server version: Apache/2.4.25 (Raspbian)
Server built: 2017-09-19T18:58:57

PHP version (eg, 7.1):

php -v
PHP 7.0.27-0+deb9u1 (cli) (built: Jan 5 2018 13:51:52) ( NTS )
Copyright (c) 1997-2017 The PHP Group
Zend Engine v3.0.0, Copyright (c) 1998-2017 Zend Technologies
with Zend OPcache v7.0.27-0+deb9u1, Copyright (c) 1999-2017, by Zend Technologies

Config

sudo -u www-data php /var/www/nextcloud/occ config:list
{
“system”: {
“instanceid”: “REMOVED SENSITIVE VALUE”,
“passwordsalt”: “REMOVED SENSITIVE VALUE”,
“secret”: “REMOVED SENSITIVE VALUE”,
“trusted_domains”: [
“”,
glqbla.net
],
“datadirectory”: “REMOVED SENSITIVE VALUE”,
“overwrite.cli.url”: “https://blabla.net/nextcloud”,
“default_language”: “de”,
“dbtype”: “mysql”,
“version”: “13.0.1.1”,
“dbname”: “REMOVED SENSITIVE VALUE”,
“dbhost”: “REMOVED SENSITIVE VALUE”,
“dbport”: “”,
“dbtableprefix”: “oc_”,
“dbuser”: “REMOVED SENSITIVE VALUE”,
“dbpassword”: “REMOVED SENSITIVE VALUE”,
“installed”: true,
“maintenance”: false,
“theme”: “”,
“logtimezone”: “Europe/Berlin”,
“mail_from_address”: “REMOVED SENSITIVE VALUE”,
“mail_smtpmode”: “smtp”,
“mail_domain”: “REMOVED SENSITIVE VALUE”,
“mail_smtpsecure”: “tls”,
“mail_smtpauthtype”: “LOGIN”,
“mail_smtphost”: “REMOVED SENSITIVE VALUE”,
“mail_smtpport”: “587”,
“mail_smtpauth”: 1,
“mail_smtpname”: “REMOVED SENSITIVE VALUE”,
“mail_smtppassword”: “REMOVED SENSITIVE VALUE”,
“loglevel”: 0,
“memcache.distributed”: “\OC\Memcache\Redis”,
“memcache.locking”: “\OC\Memcache\Redis”,
“memcache.local”: “\OC\Memcache\APCu”,
“redis”: {
“host”: “REMOVED SENSITIVE VALUE”,
“port”: “0”,
“dbindex”: 16,
“password”: “REMOVED SENSITIVE VALUE”,
“timeout”: 1.5
},
“quota_include_external_storage”: true,
“enabledPreviewProviders”: [
“OC\Preview\Image”,
“OC\Preview\MP3”,
“OC\Preview\TXT”,
“OC\Preview\MarkDown”,
“OC\Preview\Epub”,
“OC\Preview\FB2”,
“OC\Preview\PDF”,
“OC\Preview\OpenDocument”,
“OC\Preview\StarOffice”,
“OC\Preview\MSOfficeDoc”,
“OC\Preview\MSOffice2003”,
“OC\Preview\MSOffice2007”
],
“updater.release.channel”: “stable”
},

log from Webgui
Error Undefined index: ownerDisplayName at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#209 29 minutes ago
Error Undefined index: owner at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#208 29 minutes ago
Error Undefined index: quota at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#186 29 minutes ago
Error Undefined index: quota at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#180 29 minutes ago
Info Login attempt: “User1” 30 minutes ago
Error Undefined index: ownerDisplayName at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#209 30 minutes ago
Error Undefined index: owner at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#208 30 minutes ago
Error Undefined index: quota at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#186 30 minutes ago
Error Undefined index: quota at /var/www/nextcloud/apps/files/lib/Controller/ViewController.php#180 30 minutes ago
Error Undefined index: quota at /var/www/nextcloud/lib/private/Settings/Personal/PersonalInfo.php#120 31 minutes ago
Error Undefined index: quota at /var/www/nextcloud/lib/private/Settings/Personal/PersonalInfo.php#107 31 minutes ago
Error issuetemplate
Core: /var/www/nextcloud

USB PATRIOT (external data folder with symlink)

WebGUI Quota (corresponds correct to folder "files" in User1 (marked folder in picture above with 25,2 GiB, so it´s still correct))

The problem now is, that external HDD (Elements) is not recognized.

df -h

blkid

blkid
/dev/mmcblk0p1: LABEL=“boot” UUID=“CDD4-B453” TYPE=“vfat” PARTUUID=“49477e12-01”
/dev/mmcblk0p2: LABEL=“rootfs” UUID=“72bfc10d-73ec-4d9e-a54a-1cc507ee7ed2” TYPE=“ext4” PARTUUID=“49477e12-02”
/dev/mmcblk0: PTUUID=“49477e12” PTTYPE=“dos”
/dev/sda: LABEL=“PATRIOT” UUID=“54c4394d-5c03-427c-9296-b81e0806b5a8” TYPE=“ext4”
/dev/sdb1: LABEL=“Elements” UUID=“A270C02670BFFED3” TYPE=“ntfs” PARTUUID=“00098768-01”

Another problem is, the quota exceeds max user quota when sharing stuff in groups to the user and he is not able to add new files, especially when the shared folder contains stuff from HDD Elements.
Cheers.