Files and Folders shown twice in Web UI

We have the problem that in some folders, all the files and sub-folders are shown twice in the web user interface, sometimes with conflicting information about the size or modification date, see the following screenshot:

I tried to run occ files:cleanup as well as occ files:scan --path="/user/files/00000 Sales", but it did not change anything.

We had problems with file staying locked, so I enabled memory caching (redis) for content and file locking, and cleared the oc_file_locks table in the database, but that didn’t change some files and folders being shown twice.

How can we fix this?

Nextcloud version: 11.0.3
Operating system and version: Ubuntu 16.04.2 LTS
Apache or nginx version: Apache 2.4.18
PHP version (eg, 5.6): 7.0.15
Is this the first time you’ve seen this error?: yes

Can you reliably replicate it? (If so, please outline steps):
Well, every time I visit the folder in the Web UI, I see the fies/folders twice. But I have no idea how to reproduce it in new folders.

The issue you are facing:
It’s very confusing for users of the web interface

The output of your Nextcloud log in Admin > Logging:
lots of other messages concerning other files (accesses, logins, …), but nothing directly related when I open this folder in the Web UI.

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

$CONFIG = array (
  'instanceid' => '*****',
  'passwordsalt' => '*****',
  'secret' => '*****',
  'trusted_domains' => 
  array (
    0 => '*****.com',
    1 => '*****.com',
    2 => '*****.com',
  'datadirectory' => '/srv/*****/data',
  'overwrite.cli.url' => 'https://*****',
  'dbtype' => 'mysql',
  'version' => '',
  'dbname' => '*****',
  'dbhost' => 'localhost',
  'dbtableprefix' => 'oc_',
  'dbuser' => '******',
  'dbpassword' => '*****',
  'logtimezone' => 'UTC',
  'installed' => true,
  'mail_smtpmode' => 'smtp',
  'mail_smtpsecure' => 'tls',
  'mail_from_address' => '****',
  'mail_domain' => '*****',
  'mail_smtpauthtype' => 'LOGIN',
  'mail_smtpauth' => 1,
  'mail_smtphost' => '*****.com',
  'mail_smtpname' => '*****@*****.com',
  'mail_smtppassword' => '*****',
  'theme' => '',
  'loglevel' => 1,
  'maintenance' => false,
  'updater.secret' => '*****',
  '' => 'stable',
  'memcache.local' => '\OC\Memcache\Redis',
  'redis' => array(
    'host' => 'localhost',
    'port' => 6379,
  'memcache.locking' => '\OC\Memcache\Redis',

The output of your Apache/nginx/system log in /var/log/____:
Apache’s access.log just logs the request, the error.log doesn’t log anything when refreshing the page.

After my initial search did not find any related issue, I think now I found one:

This delegates to which sounds reasonable that we ran into the same problem.