Updater offers older version

Nextcloud version: 13.02
Shared host

The issue you are facing:
I tried to upgrade my nextcloud installation from 12.04. The webupdater couldn’t find new updates so I did it manually. I copyied nextcloud 13.02 onto the webspace and copeid data/ and config/ from the old installation. The update worked, but now the updater still says

Version

Nextcloud 13.0.2

A new version is available: Nextcloud 12.0.4

When I open the updater it says

Initializing

Current version is 13.0.2.
and quits.

Is this the first time you’ve seen this error? Y
I already updated from 10 to 11 automatically, so it did work before

The output of your Nextcloud log in Admin > Logging:

|Error|internet_connection_check|GuzzleHttp\Exception\ConnectException: cURL error 35: gnutls_handshake() failed: A TLS fatal alert has been received.|2018-05-11T15:09:47+0200|
|---|---|---|---|
|Error|internet_connection_check|GuzzleHttp\Exception\ConnectException: cURL error 35: gnutls_handshake() failed: A TLS fatal alert has been received.|2018-05-11T15:09:43+0200|
|Error|internet_connection_check|GuzzleHttp\Exception\ConnectException: cURL error 35: gnutls_handshake() failed: A TLS fatal alert has been received.|2018-05-11T15:03:11+0200|
|Error|PHP|Undefined index: eol at /var/www/web/html/mydomain/nextcloud/apps/updatenotification/lib/UpdateChecker.php#51|2018-05-11T15:03:09+0200|

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

<?php
$CONFIG = array (
  'instanceid' => 'ocnvj87vepfs',
  'passwordsalt' => 'BW4aKW7iwBaryyJp9FLvl4A6yAXlXp',
  'secret' => 'YBQ7DEEN6+dg2MBiVkGN7UBOsFPuikZ9IsE8ziB4npaLAyyo',
  'trusted_domains' => 
  array (
    0 => 'mydomain.com',
    1 => 'nextcloud.mydomain.com,
  ),
  'datadirectory' => '/var/www/web/html/mydomain/nextcloud/data',
  'overwrite.cli.url' => 'https://nextcloud.mydomain.com',
  'dbtype' => 'sqlite3',
  'version' => '13.0.2.1',
  'logtimezone' => 'UTC',
  'installed' => true,
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 2,
  'mail_domain' => 'mydomain.com',
  'mail_from_address' =>adress',
  'mail_smtpmode' => 'smtp',
  'mail_smtphost' => 'maildomain',
  'mail_smtpauth' => 1,
  'mail_smtpname' => 'username',
  'mail_smtppassword' => 'pass',
  'mail_smtpport' => '587',
  'mail_smtpsecure' => 'tls',
  'mail_smtpauthtype' => 'LOGIN',
  'updater.secret' => '$2y$10$luve8BJX9e5qh91z2P4Ruu/Zr8eabbYgxaAkKakgByuYh8s/wA/Ta',
  'updater.release.channel' => 'stable',
);

Any ideas? Does nobody else have this problem? I’m thinking about a new installation because I don’t want to update manually all the time.