API crashing due to Unexpected end of stream on com.android.okhttp.Address

I developed a mobile app and an ASP.Net Core Web API for a project we have in our enterprise. When I try to run the app accessing my API, it crashes. In debug, I keep getting this exception (sometimes the number at the end changes, but I don't know what it means):

System.Exception: 'unexpected end of stream on com.android.okhttp.Address@91704093'

A friend recommended me to run the app while running dotnet MyAPI.dll --urls "http://*:myportnumber command on cmd in our API server. Here's the result:

dotnet MyAPI.dll --urls "http://*:myportnumber"
info: Microsoft.Hosting.Lifetime[0]
      Now listening on: http://[::]:myportnumber
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
      Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
      Content root path: C:\IISsites\MyAPIFolder
warn: Microsoft.AspNetCore.HttpsPolicy.HttpsRedirectionMiddleware[3]
      Failed to determine the https port for redirect.
info: Microsoft.Hosting.Lifetime[0]
      Application is shutting down...

There is this small warning, which I removed by following this solution, but then the API access on the app began to take forever to load, so I decided to just ignore the warning.

While this command is in execution on the server, the API works like a charm on the app, but when I stop running it, the exception returns or the app crashes.

In order to solve the exception, I have tried to:

1. (source) Add android:usesCleartextTraffic="true" android:networkSecurityConfig="@xml/network_security_config" to the app's AndroidManifest.xml and create a new xml file in Resources\xml\network_security_config.xml with the following code:

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <domain-config cleartextTrafficPermitted="false">
        <domain includeSubdomains="true">https://ourenterpriseurl.com.br/api</domain>
    </domain-config>
</network-security-config>

2. (source) Set the HttpClient implementation to Android and the SSL/TLS implementation to Native TLS1.2+ on Project Options > Android Options > Advanced Options;

3. (source) Edit the CreateHostBuilder method on Program.cs like this:

public static IHostBuilder CreateHostBuilder(string[] args)
{
    var config = new ConfigurationBuilder()
        .SetBasePath(Directory.GetCurrentDirectory())
        .AddJsonFile("hostsettings.json", optional: true)
        .AddCommandLine(args)
        .Build();

    return Host.CreateDefaultBuilder(args)
        .ConfigureWebHostDefaults(webBuilder =>
        {
            webBuilder.UseConfiguration(config)
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseUrls("http://*:myportnumber")
            .UseStartup<Startup>();
        });
}

The content of hostsettings.json is:

{
  "urls": "http://*:myportnumber"
}

So, how do I get rid of this exception in order to make my project work?

ABOUT THE API: it is developed in ASP.Net Core 5.0; accesses stored procedures in our SQL Server database with it's own SQL credentials; it is published on the IIS of an OnPremises server of ours; it becomes publicly available for our mobile app via FortiWeb; the connection string is encrypted using Aes and CryptoStream and the resulting string is written in appsettings.json; the connection string is decrypted in Startup.cs.