In today’s daf, on Gittin 29b, something strange occurs with the Mishnah in the Soncino printing:
That is, all other printings and manuscripts have the following Mishnah:
מַתְנִי׳ הַמֵּבִיא גֵּט מִמְּדִינַת הַיָּם, וְחָלָה – עוֹשֶׂה שָׁלִיחַ בְּבֵית דִּין וּמְשַׁלְּחוֹ, וְאוֹמֵר לִפְנֵיהֶם: ״בְּפָנַי נִכְתַּב וּבְפָנַי נֶחְתַּם״; וְאֵין שָׁלִיחַ אַחֲרוֹן צָרִיךְ שֶׁיֹּאמַר ״בְּפָנַי נִכְתַּב וּבְפָנַי נֶחְתַּם״, אֶלָּא אוֹמֵר: שְׁלִיחַ בֵּית דִּין אֲנִי.
MISHNA: With regard to an agent who is bringing a bill of divorce from a country overseas, who must attest to the fact that he witnessed the writing and signing of the bill of divorce, and he became sick and cannot complete his agency, he appoints another agent in court and sends him. And the first agent says before the court: It was written in my presence and it was signed in my presence, and on the basis of this the court deems the bill of divorce to be valid. And the final agent does not need to say: It was written in my presence and it was signed in my presence. Rather, it is sufficient that he says: I am an agent of the court.
but in the Soncino printing, it is this:
The specific printed volume scanned by Hachi Garsinan has someone’s edits in ink noting the error and fixing it.
What appears to have happened is dittography, an accidental repetition of an earlier Mishnah, and therefore the skipping of the correct Mishnah. In part, because both Mishnayot begin with Hameivi Get. Instead of the Mishnah of Gittin 3:5, we are given Gittin 3:3. That Mishnah appears on Gittin 27a, and Soncino has the same (and now correct) Mishnah there.
I think what occurred was a collation problem. They had the text of the gemara, and the had the text of Mishnayot, and these were separate. Indeed, if you look at certain old manuscripts, like Munich 95, you don’t have a flowing text from Mishnah to Gemara. Rather, the Mishnah appears separately. And that is partly the role of the piskaot, to show what portion of gemara accords to which portion of Mishnah. And it is also perhaps why you have different cuts (where the Mishnah ends and gemara begins) from the Rif and Rosh to what we have in our printed gemara.
So I would speculate that the printer said on 29b, OK, the Mishnah is supposed to go here, and it begins hameivi get. And then they fetched the wrong Mishnah, and they placed it there.