Why in some translations of Romans 16 there is "amen" twice in the text?

Question

I was reading some crazy theory that New Testament was created by Romans when I stumbled upon something interesting. Author(s) of that theory pointed out that in Letter to Romans there is double "amen" (and they claimed that after first amen it was Phoebe mentioned in the letter that written the rest):

Romans 16, 21-25 (KJV)

21 Timotheus my workfellow, and Lucius, and Jason, and Sosipater, my kinsmen, salute you. 22 I Tertius, who wrote this epistle, salute you in the Lord. 23 Gaius mine host, and of the whole church, saluteth you. Erastus the chamberlain of the city saluteth you, and Quartus a brother. 24 The grace of our Lord Jesus Christ be with you all. Amen.

25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began, 26 but now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith: 27 to God only wise, be glory through Jesus Christ for ever. Amen.

I noticed that first Amen in absent in modern translations. Could you explain me why?

Answer 1

The modern translation seems best. The best theory I have heard is that the reason for the corruption (some manuscripts have incorrectly added the doxology statement in verse 24) is that this was a incomplete repair of a larger corruption attempting to remove the original doxology.

According to ancient debates over some differences in manuscripts, apparently some were corrupted by removing 16:25-27 and then inserting a fake doxology in its place. When this was corrected by manuscripts that maintained the original doxology from Paul, possibly the additional one was not properly removed due to lack of proof of the addition.

Because of their anti-Rome and anti-Old Testament bias Marcion and his followers were not favorably impressed with references to Rome in 1:7, 15, and to the Old Testament in 15:4, 8, 9 f. Some believe that it was Marcion himself who mutilated the text of Romans. It was Origen who stated, “Marcion, by whom the evangelical and apostolic writings were falsified, removed this section [16:25–27] completely from the epistle, and not only so, but deleted everything from that place where it is written, ‘whatsoever is not of faith is sin,’ [14:23] right to the end.”441 But whether the removal of the final two chapters of Romans was done by the heretic himself, as Origen believed, or by others, makes little difference. (Baker New Testament, Romans, p519)

According to Bob Utley, Professor of Hermeneutics, Early Greek Manuscripts do not have verse 24 supporting the idea that someone added it and is now correctly removed:

This verse is not present in the early Greek manuscripts, P46, 61, א, A, B, C, and 0150. It is found in some Greek manuscripts after 16:23 and others after 16:27. It is obviously not original with Paul. It is omitted in the NASB, NRSV, TEV and NJB translations. The UBS4 rates its omission as “certain” (A). It is an attempted close to the letter and is related to the problem of the closing doxology being at the end of chapter 14, 15, and 16 in various ancient Greek texts. (The Gospel According to Paul: Romans, Bob Utley)

As usual, although these minor flaws in the New Testament are interesting and worth investigating they manifest the remarkable integrity of the scriptures do to their few numbers and negligible impact on the doctrines contained in them.