Failure adding Comments to Files

Nextcloud version : 13.0.4
Operating system and version : Cent OS 7
Apache or nginx version : 2.4.6-80.el7.centos.x86_64
PHP version : 7.1.18

The issue you are facing:
Adding Comments to Files in larger Folder structure with a few users about(15) fails.
Script runs for a few minutes(circle turns), then nextcloud show error massage to user.
Tested with several browsers and user.

Is this the first time you’ve seen this error? : No since a few nextcloud version

Steps to replicate it:

  1. Folder Structure Projects\Files Project A\Group 44\Last Meeting 334\Todos\Max\map1.xls
  2. Add Comment to map1.xls

The output of your Nextcloud log in Admin > Logging:

nothing info level debug

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

$CONFIG = array (
  'instanceid' => 'XXX',
  'passwordsalt' => 'XXX',
  'secret' => 'XXX',
  'trusted_domains' =>
  array (
    0 => '',
  'datadirectory' => '/daten/owndata',
  'overwrite.cli.url' => '',
  'dbtype' => 'mysql',
  'version' => '',
  'dbname' => 'XXX',
  'dbhost' => 'localhost',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'XXX',
  'dbpassword' => 'XXX',
  'logtimezone' => 'Europe/Berlin',
  'installed' => true,
  'ldapIgnoreNamingRules' => false,
  'preview_libreoffice_path' => '/usr/bin/libreoffice',
  'mail_from_address' => 'cloud',
  'mail_smtpmode' => 'smtp',
  'mail_domain' => '',
  'mail_send_plaintext_only' => true,
  'loglevel' => 3,
  'log_rotate_size' => 104857600,
  'appstore.experimental.enabled' => true,
  'maintenance' => false,
  'ldapProviderFactory' => '\\OCA\\User_LDAP\\LDAPProviderFactory',
  'mail_smtphost' => 'mail',
  'mail_smtpport' => '25',
  'memcache.local' => '\\OC\\Memcache\\APCu',
  '' => 'stable',
  '' => false,
  'theme' => '',
  'updater.secret' => '',

The output of your Apache/nginx/system log in /var/log/____:

nothing :frowning: 

I have a similar problem: After editing a comment I sumbit it. Circle does not stop turning, I just continue commenting another file in the same folder. After several such submits server slows down. Reloading the page brings error messages, one for each comment, saying comment could not be saved.
But all comments are saved!
Face this problem now with Nextcloud 13.0.5, but had it with several earlier versions, including 12.x.y. Self hosted on Linux.