mscorlib conflict between versions

Hello

I have a Xamarin Forms Shared Project which can build and deploy without errors. However, the following build warning have appeared:

There was a conflict between "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" and "mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e".
1> No way to resolve conflict between "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" and "mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e". Choosing "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" arbitrarily.

The build warning seems to have appeared after updating Visual Studio and I cannot get rid of it.
I have tried cleaning the project, removing bin folder, .vs folder and building a new project with the same dependencies but that does not replicate the warning.

I have found other posts with a similar issue to this but I do not know if those problems are related:
https://developercommunity.visualstudio.com/content/problem/45257/no-way-to-resolve-conflict-between-mscorlib-versio.html
https://forums.xamarin.com/discussion/71781/how-to-get-rid-of-there-was-a-conflict-between-warnings-reported-between-different-packages
https://forums.xamarin.com/discussion/100868/mscorlib-version-2-0-5-0-vs-version-4-0-0-0#latest

I have the following versions:

Microsoft Visual Studio Enterprise 2017
Version 15.3.2
VisualStudio.15.Release/15.3.2+26730.10
Microsoft .NET Framework
Version 4.6.01586

Installed Version: Enterprise

Architecture Diagrams and Analysis Tools 00369-60000-00001-AA938
Microsoft Architecture Diagrams and Analysis Tools

Visual Basic 2017 00369-60000-00001-AA938
Microsoft Visual Basic 2017

Visual C# 2017 00369-60000-00001-AA938
Microsoft Visual C# 2017

Visual F# 4.1 00369-60000-00001-AA938
Microsoft Visual F# 4.1

Application Insights Tools for Visual Studio Package 8.8.00712.1
Application Insights Tools for Visual Studio

ASP.NET and Web Tools 2017 15.0.30726.0
ASP.NET and Web Tools 2017

ASP.NET Core Razor Language Services 1.0
Provides languages services for ASP.NET Core Razor.

ASP.NET Template Engine 2017 15.0.30726.0
ASP.NET Template Engine 2017

ASP.NET Web Frameworks and Tools 2017 5.2.50601.0
For additional information, visit https://www.asp.net/

Azure App Service Tools v3.0.0 15.0.30728.0
Azure App Service Tools v3.0.0

Common Azure Tools 1.10
Provides common services for use by Azure Mobile Services and Microsoft Azure Tools.

JavaScript Language Service 2.0
JavaScript Language Service

JetBrains ReSharper Ultimate 2017.1.3 Build 108.0.20170613.154143
JetBrains ReSharper Ultimate package for Microsoft Visual Studio. For more information about ReSharper Ultimate, visit http://www.jetbrains.com/resharper. Copyright © 2017 JetBrains, Inc.

Merq 1.1.17-rc (cba4571)
Command Bus, Event Stream and Async Manager for Visual Studio extensions.

Microsoft Azure Tools 2.9
Microsoft Azure Tools for Microsoft Visual Studio 2017 - v2.9.50719.1

Microsoft Continuous Delivery Tools for Visual Studio 0.3
Simplifying the configuration of continuous build integration and continuous build delivery from within the Visual Studio IDE.

Microsoft JVM Debugger 1.0
Provides support for connecting the Visual Studio debugger to JDWP compatible Java Virtual Machines

Microsoft MI-Based Debugger 1.0
Provides support for connecting Visual Studio to MI compatible debuggers

Mono Debugging for Visual Studio 4.6.8-pre (ec7034f)
Support for debugging Mono processes with Visual Studio.

NuGet Package Manager 4.3.0
NuGet Package Manager in Visual Studio. For more information about NuGet, visit http://docs.nuget.org/.

SQL Server Data Tools 15.1.61707.200
Microsoft SQL Server Data Tools

TypeScript 2.3.4.0
TypeScript tools for Visual Studio

Visual Studio Code Debug Adapter Host Package 1.0
Interop layer for hosting Visual Studio Code debug adapters in Visual Studio

Xamarin 4.6.0.299 (b63523e27)
Visual Studio extension to enable development for Xamarin.iOS and Xamarin.Android.

Xamarin.Android SDK 7.4.0.21 (2851083)
Xamarin.Android Reference Assemblies and MSBuild support.

Xamarin.iOS and Xamarin.Mac SDK 10.12.0.20 (80b8487)
Xamarin.iOS and Xamarin.Mac Reference Assemblies and MSBuild support.

I would like to know the cause of this, and if it is a serious problem that should be fixed?

I have attached the full warning

Thanks in advance