Project .sln Generates Incorrectly (Contains Duplicate Projects).

The .sln generated when I open my Unity project is not correct. It contains multiple entries for the same projects. Here is part of the solution:

Microsoft Visual Studio Solution File, Format Version 12.00
# Visual Studio 2017
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test", "Test.csproj", "{79442293-7E96-307B-F9DE-2D63F40DDE1B}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Plugins", "Test.Plugins.csproj", "{3259965F-0940-4142-FD72-0349595FD329}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test", "Test.csproj", "{79442293-7E96-307B-F9DE-2D63F40DDE1B}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Editor", "Test.Editor.csproj", "{4321CCB0-2C17-BCF8-7A90-4E57C8FCD09F}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Editor", "Test.Editor.csproj", "{4321CCB0-2C17-BCF8-7A90-4E57C8FCD09F}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Editor.Plugins", "Test.Editor.Plugins.csproj", "{807156FE-13B3-1155-556E-7F8106262C5C}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Test.Editor", "Test.Editor.csproj", "{4321CCB0-2C17-BCF8-7A90-4E57C8FCD09F}"
EndProject

I’ve tried deleting the .sln, but it always regenerates the same way.

How can I fix this?

Thanks.

Upgrading the VS 2017 to the latest version fixed the problem.