Luther Privately Admitted He Was Wrong About the Lord's Supper?

On a discussion board I frequent someone mentioned "a myth which survived for centuries that Luther privately admitted he was wrong about the Supper but didn't want to admit it publicly because people might doubt his other doctrines," and further that "Schaff, a Reformed historian and polemicist, found it necessary or desirable to mention the myth and refute it in the nineteenth century."

These comments coincided with my recent entry, Luther Acknowledged His Errors on the Real Presence in the Lord's Supper? so I was intrigued enough to track down what  Philip Schaff stated. The comments in question appear in either Vol. 6 or 7 of Schaff's History of the Christian Church, "Modern Christianity: The German Reformation" depending on what edition is utilized. Google Books Second Revised Edition of 1916 has the comment at 6:659. After documenting Luther's last attacks on the Sacramentarians and his lifelong adherence to the Real Presence in the Lord's Supper, Schaff states:

In view of these last utterances we must, reluctantly, refuse credit to the story that Luther before his death remarked to Melanchthon: “Dear Philip, I confess that the matter of the Lord’s Supper has been overdone;"(1) and that, on being asked to correct the evil, and to restore peace to the church, he replied: “I often thought of it; but then people might lose confidence in my whole doctrine. I leave the matter in the hands of the Lord. Do what you can after my death." (2)

(1) “Der Sache vom Abendmahl ist viel zu viel gethan."

(2) Hardenberg, a Reformed minister at Bremen (d. 1574), reported such a conversation as coming from the lips of his friend Melanchthon; but Melanchthon nowhere alludes to it. Stahelin (John Calvin, I. 228 sq.) accepts, Kostlin (M.L., II. 627) rejects the report, as resting on some misunderstanding. So also C. Bertheau in the article “Hardenberg” in Herzog’, V. 596 sq. Comp. Diestelmann, Die letzte Unterredung Luthers mit Melanchthon uber den Abendmahlsstreit, Gottingen, 1874; Kostlin’s review of Diestelmann, in the “Studien und Kritiken," 1876, p. 385 sqq.; and Walte in the “Jahrb. fur prot. Theol.," 1883. It is a pity that the story cannot be sufficiently authenticated, for it certainly expresses what ought to have been Luther’s last confession on the subject.

Upon a little further digging I came across more details from The Lutheran Church Review:

DID LUTHER CHANGE HIS VIEW?
Already during Luther's lifetime the rumor was circulated that he had after all abandoned his former view in regard to the Lord's Supper. This caused him to publish one more declaration on the subject in 1544. Besides it was no secret to him that his great associate Melanchthon, “with a dangerous yearning for peace which must have been hollow and transient” (Krauth), had left the position which he had so clearly expressed in the Augsburg Confession of 1530. Moreover, Luther to his greatest indignation heard that one of his former students and housemates, Dévay, had smuggled the Reformed doctrine under his (Luther's) name into Hungary. These and similar provocations caused him to write this last declaration on the subject in the sharpest possible manner. In this “Short Confession” he does not argue; he simply reaffirms in the strongest possible terms his faith in the real presence; he also expresses his total and final separation from the Sacramentarians and their doctrine. “Standing on the brink of the grave and in view of the judgment-seat, he solemnly condemns all enemies of the sacrament wherever they are.” (Schaff). Still before a quarter of a century had passed the rumor again spread that Luther shortly before his death regretted the position he had taken against the Swiss. Hardenberg, a Reformed minister at Bremen, declared under oath that he had heard from the lips of Melanchthon that Luther had requested Melanchthon to come to him, and had then said: “Dear Philip, I confess that the matter of the Lord's Supper has been overdone.”—DerSache vom Abendmahl ist viel zu wicl gethan. And that on being asked to correct the evil he replied: “I often thought of it; but then people might lose confidence in my whole doctrine. I leave the matter in the hands of the Lord. Do what you can after my death.” Melanchthon never quotes such words in his writings or letters. Are they historical or not? Schaff very reluctantly rejects the correctness of the report, but adds in a foot-note: “It is a pity that this story cannot be sufficiently authenticated, for it certainly expresses what ought to have been Luther's last confession on the subject.” Several books and many articles were written on this question. The latest investigation is by Prof. Hausleiter, of Greifswald, in the Neue Kirchliche Zeitschrift, Vol. 1899. He proves (as we think beyond doubt) by unearthing new and so far unknown material that the words, at least in substance, came from Luther and Melanchthon, but referred to an entirely different subject. He proves that already during Luther's life-time the publication of Luther's collected writings was commenced (the Wittenberg Edition) though the printing of the first volume was not completed until two years after his death. In this first volume also the writings concerning the Sacrament were to be contained. Bucer, who now sided with Luther, desired that the scorching words of Luther referring to him and his miserable tactics (described in Article I.) should be omitted. He did not venture to ask this of Luther himself. but urged his request through the Elector and Melanchthon. Luther at first refused point blank, but a few days before leaving Wittenberg for Eisleben, where he died, consented to permit the change. The words quoted by Hardenberg referred to this omission. For this reason the words were omitted in the first Wittenberg edition. We have clear and very positive declarations of Luther made shortly before his death showing that he was far from abandoning or modifying his conviction in regard to the Lord's Supper. He remained steadfast in his confession unto the end.

That there have been historians that think Luther changed his view can be seen by the following example from Paul Emil Henry's  The Life and Times of John Calvin, the Great Reformer, Volume 2 (1849):

The testimony of Dr. Alesius Scotus, a professor at Leipzig, and the friend of Luther and Melancthon, is well known, and has been often printed. In his answer to Ruard Tapper's defence of the Louvain articles, he says, "They do as if they were ignorant of what Luther said to Philip, ere he set out for his native province, where he died. Philip related it to many, and in various ways, that Luther, unasked, said, 'I own that too much has been done respecting the sacrament:' and when Philip answered, 'Let us then, my good doctor, for the sake of the churches, publish some pacific treatise, in which we may clearly unfold our views'—Luther replied, 'My Philip, I have thought anxiously on this matter; but as I might throw suspicion upon the whole doctrine, I will only commend it to the good care of God. Do you do something after my death.' These words were written down from Melancthon's own mouth." It was the wish of the latter to mention the subject in his testament, but he died too soon. The witness of Dr. Alesius, who had the account from Melancthon himself, is therefore valuable. It seems certain, that as Zwingli had a deeper insight into the sacrament in the latter years of his life, Luther also, a year before his death, was of one faith and of one mind with Calvin. He regarded him as a brother, and viewed his doctrine as fitted to restore union to the distracted church. And as Luther inclined to Calvin, so did Calvin to Luther. He twice declared his assent to the Augsburg Confession, and stated that, in his opinion, the formulary of the Zurich Union contained whatever was found in the Confession.