Unexpected behavior of LINQ Except()

I have encountered a strange bahavior of LINQ Except method which I don't understand. I can totally rewrite my code differently so that it works, that is not my problem. I just want to understand why it fails as it is:

public void MyMethod(MyClass whatever, params object[] values){ // called with values = [ "mystr1", "mystr2", true, true ] 
  var valuesOfType = values.OfType<MyType>().ToList(); // valuesOfType is Empty List Count = 0
  values = values.Except(valuesOfType ).ToArray(); // values = [ "mystr1", "mystr2", true ] 
}

So last element of values is gone by applying Except() with an empty list! How is this possible? I reran in debugger immidiate window the line again, it was not trunkated to 2 elements. Self assignment to values is not a problem, I tried it with another variable, it still trunkates. What is happening here?

PS: MyType is just a simple type with one get property.

Although the question is already answered, here is a reproduceable console app, if somebody should want to see it for himself:

namespace ConsoleApp1
{
    using System;
    using System.Linq;

    class Program
    {
        static void Main(string[] args)
        {
            var para = new object[] {"str1", "str2", true, true};
            var temp = new TestClass(new Dummy1(), para);
        }

        public class TestClass
        {
            public TestClass(Dummy1 dummy1, params object[] values)
            {
                var valuesOfType = values.OfType<Dummy2>().ToList();
                values = values.Except(valuesOfType).ToArray();

                foreach (var value in values)
                {
                    Console.WriteLine(value);
                }
                
                Console.ReadKey();
            }
        }

        public class Dummy1
        {
        }

        public class Dummy2
        {
        }
    }
}