foreach over "Xover" results in next client.Head command returning wrong data

[devedse]

                var xoverResponse = client.Xover(new NntpArticleRange(firstArticle, lastArticle));

                foreach (var header in xoverResponse.Lines)
                {
                    var messageId = "RkVnY3k4RDNak6oLP4abnE5fd4s@spot.net";
                    var head2 = client.Head(new NntpMessageId(messageId));
                    var head3 = client.Head(new NntpMessageId(messageId));
                }

In this scenario head2 != head3. It's in fact Lines[1] and Lines[2].