The Rambam, in his introduction to the Mishnah (link), writes that there were never debates in the Talmud regarding oral traditions from Sinai, that one part forgot or was mistaken about and the other correct. This has led many to conclude that the Rambam is of the view that oral traditions could not be forgotten and no one could make a mistake regarding them, at least in the Talmudic era. This is a very difficult claim to accept.
R. Tzvi Hirsch Chajes (Toras Nevi’im, Ma’amar Torah She-Be-Al Peh in Kol Sifrei Maharatz Chajes, vol. 1 pp. 114-115) explains that the Rambam intended something different. He meant that if there was a debate between two talmudic scholars and one claimed that his view was based on an oral tradition, then the other would immediately capitulate. Therefore, there were no debates based on forgetting an oral tradition because if one side claimed that he had a tradition for his position, the debate would end. But absent a debate, traditions can be forgotten. While this might seem like a farfetched interpretation, a careful reading of the Rambam’s words can fit nicely with this understanding. This is also the approach of R. Yitzchak Sheilat (Hakdamos Ha-Rambam La-Mishnah, p. 90).
R. Ya’akov (Gerald J.) Blidstein (Samkhus U-Meri Be-Hilkhas Ha-Rambam, pp. 47-48 n. 3) argues against this interpretation. He points out that the Rambam also says that there were no debates based on a mistake in a tradition. If someone mistakenly thought that his position was based on an oral tradition from Sinai, would he concede when his opponent said that he had an oral tradition for his position? Presumably not. To the opposite, he would stand firm in his position because he thinks he has an oral tradition supporting it.
This argument of R. Blidstein has already been addressed by R. Zvi Lampel (The Dynamic of Dispute, ch. 7). R. Lampel suggests that the Rambam meant that if a scholar thinks that his position is supported by an oral tradition but is confronted with someone claiming a tradition to the contrary, he will humbly investigate the possibility that he might be mistaken. In this very passage, the Rambam emphasizes the moral qualities of the Sages. Thus, he is suggesting that the search for truth and humility of the Sages prevented them from falling into debates based on forgetting or mistaking a tradition. Once the issue of a tradition is raised, Sages will investigate and consider whether that tradition is legitimate and, if so, they will concede.