c# – 为什么Principal.IsMemberOf()对某些组返回false negative

[TestMethod]
public void DomainComputerTest()
{
    var distinguishedName = "CN=MyMachine,DC=SomeDomain,DC=local";
    using( var pc = new PrincipalContext( ContextType.Domain,"SomeDomain.local","UserName","Password" ) )
    using( var computer = ComputerPrincipal.FindByIdentity( pc,IdentityType.DistinguishedName,distinguishedName ) )
    {
        Assert.IsNotNull( computer );
        // Get the groups for the computer.
        var groups = computer.GetGroups().Cast<GroupPrincipal>();
        foreach( var group in groups )
        {
            // Immediately turn around and test that the computer is a member of the groups it returned.
            Assert.IsTrue( computer.IsMemberOf( group ),"Computer is not member of group {0}",group.Name );
        }
    }
}

结果消息：Assert.IsTrue失败.计算机不是“域计算机”组的成员

计算机确实是“域计算机”组的成员,“GetGroups()”方法正确返回.实际上,如果您尝试将计算机添加到组中,则会抛出PrincipalExistsException.

我可以与用户和“域用户”组重现完全相同的行为.这是因为这些团体是校长团体吗？是因为这些是“默认”群组吗？

编辑添加：我们正在使用.NET 4.5.1.