nunit: NUnitEngineException : Unable to acquire remote process agent

I’m trying to start some tests with nunit3-console.exe (v3.8.0) on a virtual machine running Windows 10 (x64) but before any tests get executed NUnit stops. I get the following error messages:

Unhandled Exception: NUnit.Engine.NUnitEngineException: Failed to start remote test agent.
   at NUnit.Engine.Services.TestAgency.OnAgentExit(Object sender, EventArgs e)
   at System.Diagnostics.Process.OnExited()
   at System.Diagnostics.Process.RaiseOnExited()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading._ThreadPoolWaitOrTimerCallback.PerformWaitOrTimerCallback(Object state, Boolean timedOut)

And after a few more seconds this is shown:

1) Error :
NUnit.Engine.NUnitEngineException : Unable to acquire remote process agent
--NUnitEngineException
   at NUnit.Engine.Runners.ProcessRunner.CreateAgentAndRunner()
   at NUnit.Engine.Runners.ProcessRunner.RunTests(ITestEventListener listener, TestFilter filter)

I recently added the flag –x86 to NUnit and that’s when this issue started. I added the flag because I also added an external file (Microsoft Exression Encoder) to my test project, and it seems to be x86 only. I read (on Stackoverflow I think) that using –inprocess works. I used to have that flag but it is not compatible with –x86. So I can’t get it to work no matter how I try.

This is the command I use to run NUnit: nunit3-console.exe C:\...\GUITests.dll --x86 --where "cat == .NIGHTLY" --result="C:\...\Logs\TestResult.xml;format=nunit2"