Donloading a file called

This file is downloaded to us. Sometimes it has HTML content and other times it is undefined. Apparently when it happens it happens simultaneously to all of them at the same time. Attached evidence.`

    <!-- Roboto Typography -->
    <link href='' rel='stylesheet'>

    <!-- Hoja de Estilo principal de la Aplicación (Main Styles) -->
    <link rel="stylesheet" type="text/css" href='/static/css/style.css'>
    <link rel="stylesheet" type="text/css" href='/static/css/navbar.css'>

    <!-- Aniamte CSS -->
    <link rel="stylesheet" type="text/css" href='/static/css/animate.css'>

    <!--Font Awesome -->
    <link href="" rel="stylesheet"/>

The code continues but I have cut it.
The image is