nunit3-vs-adapter: An exception occurred while test discoverer 'NUnit3TestDiscoverer' was loading tests. Exception: Object reference not set to an instance of an object, with VS2015

• NUnit =3.12 and NUnit3TestAdapter =3.17
• Visual Studio preofessional version 15.3.3
• .net version 4.6.1
• not installed vsix

Steps to Repro

1. Create a unit test project
2. Remove mstest in nuget and install nunit and nunittestadapter latest version
3. Create a test with OneTimeSetUp attribute

using NUnit.Framework;
using System;

namespace nUnittest
{
    [TestFixture]
    public class UnitTest1
    {
       [OneTimeSetUp]
        public static void OneTimeSetUp()
        {
            Console.WriteLine("OneTimeSetUp");
        }
        [SetUp]
        public void SetUp()
        {
            Console.WriteLine("SetUp");
        }
        [TearDown]
        public void TearDown()
        {
            Console.WriteLine("TearDown");
        }
        [Test]
        public void Test()
        {
            Console.WriteLine("Test");
        }

        [OneTimeTearDown]
        public static void OneTimeTearDown()
        {
            Console.WriteLine("OneTimeTearDown");
        }
    }
}

Firs time passes,rebuild the solution>>Observe console >>error will display as mentioned in title ,test will pass,[OneTimeSetUp] / [SetUp] will not be executed packages.config

<?xml version="1.0" encoding="utf-8"?>
<packages>
  <package id="NUnit" version="3.12.0" targetFramework="net461" />
  <package id="NUnit3TestAdapter" version="3.17.0" targetFramework="net461" />
</packages>

Close VS>>Run IFix vstestcache -f >>Rebuild>> works,first time,Test runs, later exception is thrown,One time setup not runs. An exception occurred while test discoverer 'NUnit3TestDiscoverer' was loading tests. Exception: Object reference not set to an instance of an object

I tried all the workaround mentioned in https://github.com/nunit/nunit3-vs-adapter/issues/261 I tried removing the cache,works for first time,later again the same problem,cant restart everytime I changed test process acritecture to 64 still same

Note On running through nunit3-console all methods works

>nunit3-console D:\automationRepo\nUnitTest\nUnittest\bin\Debug\nUnittest.dll
NUnit Console Runner 3.11.1 (.NET 2.0)
Copyright (c) 2020 Charlie Poole, Rob Prouse
04 September 2020 18:28:56

Runtime Environment
   OS Version: Microsoft Windows NT 6.2.9200.0
   Runtime: .NET Framework CLR v4.0.30319.42000

Test Files
    D:\automationRepo\nUnitTest\nUnittest\bin\Debug\nUnittest.dll

SetUp
Test
TearDown
OneTimeSetUp
OneTimeTearDown

Run Settings
    DisposeRunners: True
    WorkDirectory: D:\automationRepo\nUnitTest\nUnittest\bin\Debug
    ImageRuntimeVersion: 4.0.30319
    ImageTargetFrameworkName: .NETFramework,Version=v4.6.1
    ImageRequiresX86: False
    ImageRequiresDefaultAppDomainAssemblyResolver: False
    RuntimeFramework: net-4.0
    NumberOfTestWorkers: 4

Test Run Summary
  Overall result: Passed
  Test Count: 1, Passed: 1, Failed: 0, Warnings: 0, Inconclusive: 0, Skipped: 0
  Start time: 2020-09-04 12:58:56Z
    End time: 2020-09-04 12:58:57Z
    Duration: 0.909 seconds

Results (nunit3) saved as TestResult.xml