Can't run NUnit tests for x86 projects

I can't run NUnit tests, after I changed the 'Platform target:' to x86.

I'm using a .NET Core 2.2 project in VisualStudio 2019 and I'm running my tests with ReSharper. The NUnit Version is 3.11.0. The following example works for x64, but does not for x86:

[TestFixture]
public class Tests
{

    [Test]
    public void Test1()
    {
        Assert.Pass();
    }
}

'Test1 Ignored: VsTest test-case is missing. Rebuild the project and try again.' So it seems like that the test is no longer identified as a NUnit Test and that the IDE tries to interpret it as a mstest?