Error NU1605 Detected package downgrade

I am experiencing the following NU1605 dependency errors in my netcoreapp2.0 console application:

NU1605  Detected package downgrade: System.Diagnostics.Debug from 4.3.0 to 4.0.11. Reference the package directly from the project to select a different version. 
 MyProject -> Colorful.Console 1.2.6 -> System.IO.FileSystem 4.0.1 -> runtime.win.System.IO.FileSystem 4.3.0 -> System.Diagnostics.Debug (>= 4.3.0) 
 MyProject -> System.Diagnostics.Debug (>= 4.0.11)

NU1605  Detected package downgrade: System.Runtime.Extensions from 4.3.0 to 4.1.0. Reference the package directly from the project to select a different version. 
 MyProject -> Colorful.Console 1.2.6 -> System.IO.FileSystem 4.0.1 -> runtime.win.System.IO.FileSystem 4.3.0 -> System.Runtime.Extensions (>= 4.3.0) 
 MyProject -> Colorful.Console 1.2.6 -> System.Runtime.Extensions (>= 4.1.0)    MyProject

NU1605  Detected package downgrade: System.Runtime.Handles from 4.3.0 to 4.0.1. Reference the package directly from the project to select a different version. 
 MyProject -> Colorful.Console 1.2.6 -> System.IO.FileSystem 4.0.1 -> runtime.win.System.IO.FileSystem 4.3.0 -> System.Runtime.Handles (>= 4.3.0) 
 MyProject -> Colorful.Console 1.2.6 -> System.IO.FileSystem 4.0.1 -> System.Runtime.Handles (>= 4.0.1)

NU1605  Detected package downgrade: System.Runtime.InteropServices from 4.3.0 to 4.1.0. Reference the package directly from the project to select a different version. 
 MyProject -> Colorful.Console 1.2.6 -> System.Console 4.0.0 -> runtime.win.System.Console 4.3.0 -> System.Runtime.InteropServices (>= 4.3.0) 
 MyProject -> Colorful.Console 1.2.6 -> System.Runtime.InteropServices (>= 4.1.0)

I have tried referencing these package versions in csproj, but this doesn't fix the problem. See csproj:

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.0</TargetFramework>
    <RuntimeIdentifier>win10-x64</RuntimeIdentifier>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Colorful.Console" Version="1.2.6" />
    <PackageReference Include="CommandLineParser" Version="2.2.1" />
    <PackageReference Include="DotSpinners" Version="1.2.0" />
    <PackageReference Include="System.Diagnostics.Debug" Version="4.0.11" />
    <PackageReference Include="System.Runtime.Extensions" Version="4.1.0" />
    <PackageReference Include="System.Runtime.Handles" Version="4.0.1" />
    <PackageReference Include="System.Runtime.InteropServices" Version="4.1.0" />
  </ItemGroup>
</Project>

And they do seem to restore fine:

The project is also referencing the Microsoft.NETCore.App 2.0 SDK.

When performing dotnet restore from the CLI, I also get the following error, which I am not sure is related:

C:\Program Files\dotnet\sdk\2.1.200\NuGet.targets(114,5): error : Failed to retrieve information about 'System.Runtime.Serialization.Formatters' from remote source 'https://mycompany.pkgs.visualstudio.com/_packaging/myid/nuget/v3/flat2/system.runtime.serialization.formatters/index.json'. [C:\MyProject\MyProject.sln]
C:\Program Files\dotnet\sdk\2.1.200\NuGet.targets(114,5): error : Response status code does not indicate success: 401 (Unauthorized). [C:\MyProject\MyProject.sln]

I have no idea why it's trying to retrieve information about 'System.Runtime.Serialization.Formatters' from our private company package repository.

NuGet.config:

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
    <add key="mycompany" value="https://mycompany.pkgs.visualstudio.com/_packaging/Stable/nuget/v3/index.json" />
  </packageSources>
  <packageSourceCredentials>
     <mycompany>
       <add key="Username" value="vsts" />
       <add key="ClearTextPassword" value="xxx" />
     </mycompany>
   </packageSourceCredentials>
  <disabledPackageSources>
    <add key="Microsoft and .NET" value="true" />
  </disabledPackageSources>
  <packageRestore>
    <add key="enabled" value="True" />
    <add key="automatic" value="True" />
  </packageRestore>
  <bindingRedirects>
    <add key="skip" value="False" />
  </bindingRedirects>
  <packageManagement>
    <add key="format" value="0" />
    <add key="disabled" value="False" />
  </packageManagement>
</configuration>

I also have the following NU1603 warning if this means anything:

NU1603  MyProject depends on System.Runtime.Handles (>= 4.1.0) but System.Runtime.Handles 4.1.0 was not found. An approximate best match of System.Runtime.Handles 4.3.0 was resolved.

I had a similar issue with a .netcoreapp2.2 console application.

The project was building successfully. However, publishing was failing with several NU1605 errors.

The problem was originated from log4net version 2.0.8. It was referenced in a .netstandard2.0 project with the following dependencies:

They were causing package downgrades in the projects referencing log4net. And during publish these warnings are treated as errors...

To solve the problem I added correct versions of these libraries via Nuget.

Finally, the publishing succeeded.

P.S. When I first added packages with the newest version of libraries, a yellow warning sign was displayed on the dependencies list as if the packages were not suitable for that project. After unloading the project and loading back the warning sign gone! (I'm using Visual Studio 2019)