CalDAV synchronizing problem (DPCalendar - CalDAV Plugin)

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Nextcloud version: 15.0.4
Operating system and version: no informations, it is part of a webhosting
Webserver: LiteSpeed
PHP version: 7.2.15

My Issue:

Since my hoster migrated some stuff on their server, I am no longer able to synchronize my nextcloud-calendars to a joomla website using DPCalendar with CalDAV Plugin. The problem exist only for that very joomla installation to a nextcloud installation which is located on the same server.

I already contacted the support for DPCalendar and he found the problem. The CalDAV server (naxtcloud) is responding with binary data. Thats what he said:
“CalDAV returns XML content or ical and no binary data. I do not know what to do as I don’t know the server. But a http request needs to return no binary data.
I’v added some debug statements and when you open now the link on view-source:https://www.pfadimorgarten.ch/programm/events?format=raw&limit=0&ids=cad-1&my=0&date-start=2019-01-28&date-end=2019-03-11&_=1550483734606, you will see that the response is some binary data.”

The problem exist only in that very configuration:

Why does the caldav server of my nextcloud installation respond to a http request from the dpcalendar caldav-plugin with binary data? Whats the problem?

The output of your Nextcloud log in Admin > Logging:

The output of your Webserver log:
217.194.61.225 - - [18/Feb/2019:18:46:18 +0100] “GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1” 200 3317 “-” “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.109 Safari/537.36”
194.150.248.71 - Piostufe [18/Feb/2019:18:46:47 +0100] “REPORT /remote.php/dav/calendars/Piostufe/piostufe/ HTTP/1.1” 207 1114 “-” “DPCalendar”
194.150.248.71 - Pfadistufe [18/Feb/2019:18:46:47 +0100] “REPORT /remote.php/dav/calendars/Pfadistufe/aushang-pfadistufe/ HTTP/1.1” 207 914 “-” “DPCalendar”
194.150.248.71 - Biberstufe [18/Feb/2019:18:46:47 +0100] “REPORT /remote.php/dav/calendars/Biberstufe/aushang-biberstufe/ HTTP/1.1” 207 1270 “-” “DPCalendar”
194.150.248.71 - Wolfstufe [18/Feb/2019:18:46:47 +0100] “REPORT /remote.php/dav/calendars/Wolfstufe/aushang-wolfstufe/ HTTP/1.1” 207 1092 “-” “DPCalendar”
217.194.61.225 - - [18/Feb/2019:18:46:48 +0100] “GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1” 200 3317 “-” “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.109 Safari/537.36”
194.150.248.71 - Biberstufe [18/Feb/2019:18:46:49 +0100] “REPORT /remote.php/dav/calendars/Biberstufe/aushang-biberstufe/ HTTP/1.1” 207 1270 “-” “DPCalendar”
194.150.248.71 - Pfadistufe [18/Feb/2019:18:46:49 +0100] “REPORT /remote.php/dav/calendars/Pfadistufe/aushang-pfadistufe/ HTTP/1.1” 207 914 “-” “DPCalendar”
194.150.248.71 - Wolfstufe [18/Feb/2019:18:46:49 +0100] “REPORT /remote.php/dav/calendars/Wolfstufe/aushang-wolfstufe/ HTTP/1.1” 207 1092 “-” “DPCalendar”
194.150.248.71 - Piostufe [18/Feb/2019:18:46:49 +0100] “REPORT /remote.php/dav/calendars/Piostufe/piostufe/ HTTP/1.1” 207 1114 “-” “DPCalendar”
194.150.248.71 - Biberstufe [18/Feb/2019:18:47:02 +0100] “REPORT /remote.php/dav/calendars/Biberstufe/aushang-biberstufe/ HTTP/1.1” 207 1270 “-” “DPCalendar”
217.194.61.225 - - [18/Feb/2019:18:47:18 +0100] “GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1” 200 3317 “-” “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.109 Safari/537.36”

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

$CONFIG = array (
  'instanceid' => 'XXXX',
  'passwordsalt' => 'XXXX',
  'secret' => 'XXXX',
  'trusted_domains' => 
  array (
    0 => 'cloud.pfadimorgarten.ch',
  ),
  'datadirectory' => '.../nextclouddata',
  'overwrite.cli.url' => 'https://cloud.pfadimorgarten.ch/nextcloud',
  'dbtype' => 'mysql',
  'version' => '15.0.4.0',
  'dbname' => 'XXXX',
  'dbhost' => 'localhost',
  'dbport' => '',
  'dbtableprefix' => 'XXX_',
  'dbuser' => 'XXXX',
  'dbpassword' => 'XXXX',
  'installed' => true,
  'theme' => '',
  'loglevel' => 2,
  'maintenance' => false,
);

Why does the caldav server of my nextcloud installation respond to a http request from the dpcalendar caldav-plugin with binary data? Whats the problem?

Any Ideas? Nobody?