Network share folders aren't visible in nextcloud sync client

Configuration details

Server

Nextcloud version: 16.0.6
Operating system and version: Debian 4.19.67
Apache or nginx version: Apache/2.4.38 (Debian)
PHP version: PHP 7.3.11

Client

Windows version: Windows Server 2016 Version 1607 (Build 14393.3474)
Nextcloud sync client version: 2.6.0stable-Win64 (Build 20190927)
Owncloud sync client version: 2.6.1 (Build 12992)

Way of working
We have a network share R:\ which is mapped on a Windows Server 2016.
On this Windows Server we have the Owncloud client installed which is syncing the folders and files of that network share to our Nextcloud Server.

Side Note: We use the owncloud client as we had a bug while syncing with the nextcloud client.
Although, the issue is occuring on both clients.

Issue description
We are facing the problem, that some folders which are on the network share R:\ don’t seem to be recogniced by the owncloud nor the nextcloud client.
Oddly, two folders are being synced by the client without any issues.

Is this the first time you’ve seen this error? Yes

Approaches

  • We checked the permissions in the security tab of the network share.
    The user which is syncing the files has access to these folders.
  • Restarted the sync client & Windows server

Steps to replicate it:
I don’t think, that this problem is easily replicable on a different system.

  1. Create a network share with files and folders.
  2. Sync the datastructure to the nextcloud.
  3. Some folders are not visible in the

Nextcloud log output (Admin > Logging):
Nothing visible, as the problem is occuring before it actually appears here.

PHP Config

Details

config.php file in /path/to/nextcloud:

<?php
$CONFIG = array (
  'instanceid' => 'XXX',
  'passwordsalt' => 'XXX',
  'secret' => 'XXX',
  'trusted_domains' => 
  array (
    0 => 'fqdn.com:80',
    1 => 'fqdn.com',
  ),
  'datadirectory' => '/data/owncloud',
  'overwrite.cli.url' => 'https://fqdn.com',
  'dbtype' => 'mysql',
  'version' => '16.0.6.1',
  'dbname' => 'database',
  'dbhost' => 'localhost',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'XXX',
  'dbpassword' => 'XXX',
  'logtimezone' => 'UTC',
  'installed' => true,
  'ldapIgnoreNamingRules' => false,
  'loglevel' => 0,
  'maintenance' => false,
  'ldapProviderFactory' => '\\OCA\\User_LDAP\\LDAPProviderFactory',
  'filelocking.enabled' => true,
  #'memcache.distributed' => '\\OC\\Memcache\\APCu',
  'memcache.local' => '\\OC\\Memcache\\APCu',
'memcache.distributed' => '\\OC\\Memcache\\Redis',
'memcache.locking' => '\\OC\\Memcache\\Redis',
'redis' =>
array (
'host' => '/var/run/redis/redis-server.sock',
'port' => 0,
'timeout' => 0,
'password' => 'XXX',
'dbindex' => 0, 
),
);

Apache log
Apache log in /var/log/apache2/error.log:

[Tue Mar 03 00:00:06.956806 2020] [ssl:warn] [pid 17384] AH01909: fqdn.com server certificate does NOT include an ID which matches the server name
[Tue Mar 03 00:00:06.957034 2020] [mpm_prefork:notice] [pid 17384] AH00163: Apache/2.4.38 (Debian) OpenSSL/1.1.1d configured -- resuming normal operations
[Tue Mar 03 00:00:06.957056 2020] [core:notice] [pid 17384] AH00094: Command line: '/usr/sbin/apache2'

Did anyone has had this problem so far?
Or is this a bug?

This Problem is still open and so far we have no solution but to change the whole folder structure, which isn’t a great solution.