Fehler in Api-Antwort: 
array(2) {
  ["url"]=>
  string(54) "https://api.spar-mit.com/public/api/check_redirect_url"
  ["http_status"]=>
  int(502)
}
Response:

Curl_response Object
(
    [url] => https://api.spar-mit.com/public/api/check_redirect_url
    [http_status] => 502
    [error_no] => 0
    [error_msg] => 
    [cache_info] => 
    [decoded:Curl_response:private] => 
    [plain_response:Curl_response:private] => 
502 Bad Gateway


502 Bad Gateway


nginx




)