The Mishnah at the start of today’s perek has a Kadar transporting goods.
מַתְנִי׳ הַשּׂוֹכֵר אֶת הָאוּמָּנִין וְהִטְעוּ זֶה אֶת זֶה – אֵין לָהֶם זֶה עַל זֶה אֶלָּא תַּרְעוֹמֶת. שָׂכַר אֶת הַחַמָּר וְאֶת הַקַּדָּר לְהָבִיא פְּרִיָיפָרִין וַחֲלִילִים לַכַּלָּה אוֹ לַמֵּת, וּפוֹעֲלִין לְהַעֲלוֹת פִּשְׁתָּנוֹ מִן הַמִּשְׁרָה, וְכׇל דָּבָר שֶׁאָבֵד וְחָזְרוּ בָּהֶן, מָקוֹם שֶׁאֵין שָׁם אָדָם – שׂוֹכֵר עֲלֵיהֶן אוֹ מַטְעָן.
MISHNA: With regard to one who hires artisans or laborers, and they deceived one another, they have nothing but a grievance against one another, and they have no financial claim against the deceptive party. If one hired a donkey driver or a potter to bring posts [piryafarin] for a canopy or flutes to play in honor of a bride or the dead, or if he hired laborers to bring up his flax from the retting tub, i.e., the container of water in which flax is placed in the first stage of the manufacture of linen, and likewise any matter that involves financial loss if not performed on time and the laborers reneged, if this occurred in a place where there is no other person to perform the task, he may hire replacements for a large fee at the expense of the first workers, or deceive them to get them to return to work.
A donkey driver - chammar - makes sense. A kaddar - potter, makes less sense. Why is he conveying. What is a “Kadar” doing back here? Tosafot say ir should be karar.
Note that almost all the manuscripts on Hachi Garsinan do have kadar. Thus (click or right click to expand image):
The one strange one is Escorial, which has a transcription with kadar in square brackets, indicating an emendation. Thus:
This was simply an omission of the word entirely, followed by the scribe adding it over the line.
The stand-alone Mishnah has kadar, rather than karar with a resh. So does Ktav Yad Kaufmann. We can tell because a resh cannot take a dagesh chazak.
So too the Mishnah in Yerushalmi.
I write all this because Tosafot state that the text should read K-R-R, with two reishes. Thus:
את הקרר - בשני רישין והוא בעל קרון ולספרים דגרסי קדר י"ל דלהכי נקט קדר לפי שקדרים רגילין להיות להם קרונות:
This would be one who owns / drives a wagon, a karon. Meanwhile the manuscripts which have kadar, Tosafot suggest a way of making it work.
This does not seem like a conjectural emendation, for they speak of Sefarim that have one version as opposed to another. Earlier, we see that the Aruch’s dictionary similarly has this:
קרר [קוטשער] (ב"מ עה) השוכר את החמר ואת הקרר להביא פרייפרין פי' בל"ר מנהיג הקרון:
Note that in Yerushalmi Kiddushin, about the professions a man shouldn’t teach his son, both karar and kadar are mentioned, and it seems that karar is the more likely and the other should perhaps be crossed out.
פִּיסְקָא. לֹא יְלַמֵּד אָדָם אֶת בְּנוֹ אוּמָּנוּת בֵּין הַנָּשִׁים כול׳. תַּנֵּי. לֹא יְלַמֵּד אָדָם אֶת בְּנוֹ חַמָּר וְגַמָּל וְסַפָּן קַדָּר קָרָר רוֹעֶה חֶנְװָנִי מִפְּנֵי שֶׁאוּמְנוּתָן אוּמָנוּת לִיסְטִין.
New paragraph. “A man should not teach his son a craft for women,” etc. It was stated: A man should not teach his son to be a donkey driver, a camel driver, a sailor, a potter, a teamster, a shepherd, or a grocer, since their occupations are those of robbers.
"both karar and kadar are mentioned, and it seems that karar is the more likely and the other should perhaps be crossed out."
I'm curious why you say that. Is there any reason why they shouldn't *both* be on the list?