error MSB4062: The "Microsoft.DotNet.Arcade.Sdk.CheckRequiredDotNetVersion"

Hi all,
Has anyone encountered this problem?
Environment:
Windows 7, Visual Studio 2017 version 15.8.1.
Workloads: .Net desktop development, .Net core cross-platformdevelopment
Individual components: All .Net framworks targeting pack from 4 to 4.6.1 including 4.6.1 SDK
The full error i'm getting when trying to build is for every project in the solution:
error MSB4062: The "Microsoft.DotNet.Arcade.Sdk.CheckRequiredDotNetVersion" task could not be loaded from the assembly ..\.nuget\packages\roslyntools.buildtasks\1.0.0-beta3.18525.2\tools\net472\RoslynTools.BuildTasks.dll. Could not load file or assembly 'file:///C:\Users\Administrator\.nuget\packages\roslyntools.buildtasks\1.0.0-beta3.18525.2\tools\net472\RoslynTools.BuildTasks.dll' or one of its dependencies. The system cannot find the file specified.

the thing is that "RoslynTools.BuildTasks.dll" does exist on my computer, but in a different directory from where it searches for.

suggestions anyone?

Start by reproducing the build on Windows 7 with Visual Studio 2017 15.8.1 and inspect the NuGet package path for roslyntools.buildtasks 1.0.0-beta3.18525.2, especially tools/net472/RoslynTools.BuildTasks.dll. Compare the resolved assembly location with the path used by Microsoft.DotNet.Arcade.Sdk.CheckRequiredDotNetVersion; done means every project loads the task successfully.

Written by the indexing model from the issue text.