Stam Mishnah Against the Majority in Temurah

The passage at Sfas Emes al HaShas (Temurah 20a) addresses the Gemara's statement that Rebbi does not see the words of Rabbi Shimon, noting that although normally the halacha would follow Rebbi as the deciding voice, the Rambam ruled like the tanna kamma instead.

Sfas Emes al HaShas (Temurah 20a) explains that the reason for this is that the whole machlokes in Temurah regarding selling a temurah is understood to be dependent upon the earlier machlokes between the tanna kamma and Rabbi Shimon in the mishnah about whether it may be sold absent a blemish (אי תמכר שלא במום), rather than being an independent dispute resolved simply by the individual-versus-majority rule.

The companion passage in Sfas Emes al HaShas (Menachot 2a) deals with an unrelated question about whether a korban must come specifically from one's own property rather than from maaser, and does not bear on how a stam mishnah of an individual is weighed against a majority in the context of selling a temurah.