Problems with ajax / json and cross-origin redirect

I have an application, in flask + javascript, that needs to query a url (on a server I do not have access to), however I get the cross-origin redirect error

  

XMLHttpRequest can not load link . Redirect from ' link ' to ' 'has been blocked by CORS policy: Request requires preflight, which is disallowed to follow cross-origin redirect.

I have tried several combinations of possible parameters in the code below (json, jsonp, plain text, async ...):

$.ajax({
    type: "GET",
    url: "https://myurl.net/api/installations/3602",
    contentType: "text/plain",
    crossDomain: true,
    dataType: "text",
    headers: {
        "Authorization": "Basic " + btoa(username + ":" + password)
    },
    success: function(data, status, jqXHR) {
        console.log(data);
    },
    error: function(jqXHR, status) {
        console.log("Error: " + status);
    },
})

The same query occurred smoothly using node / express in a test application.

Below the headers:

Response Headers
Access-Control-Allow-Credentials:true
Access-Control-Allow-Headers:x-requested-with, content-type, accept,     origin, authorization, x-csrftoken, user-agent, accept-encoding
Access-Control-Allow-Methods:GET, POST, PUT, PATCH, DELETE, OPTIONS
Access-Control-Allow-Origin:http://localhost:5000
Access-Control-Max-Age:86400
Connection:keep-alive
Content-Encoding:gzip
Content-Language:pt-br
Content-Type:text/html; charset=utf-8
Date:Tue, 14 Feb 2017 11:26:45 GMT
Server:nginx/1.6.2
Transfer-Encoding:chunked
Vary:Accept-Language
X-Frame-Options:SAMEORIGIN

Request Headers
Accept:*/*
Accept-Encoding:gzip, deflate, sdch, br
Accept-Language:en-US,en;q=0.8,pt-BR;q=0.6,pt;q=0.4
Access-Control-Request-Headers:authorization
Access-Control-Request-Method:GET
Connection:keep-alive
Host:myurl.net
Origin:http://localhost:5000
Referer:http://localhost:5000/map
User-Agent:Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like     Gecko) Chrome/54.0.2840.100 Safari/537.36 Vivaldi/1.5.658.56


Response Headers
Access-Control-Allow-Credentials:true
Access-Control-Allow-Origin:http://localhost:5000
Content-Language:pt-br
Content-Type:text/html; charset=utf-8
Date:Fri, 10 Feb 2017 18:44:21 GMT
Location:https://myurl.net/api/installations/3602/
Server:nginx/1.6.2
Vary:Accept-Language
X-Frame-Options:SAMEORIGIN

Request Headers
Provisional headers are shown
Referer:http://localhost:5000/map
User-Agent:Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.100 Safari/537.36 Vivaldi/1.5.658.56