Berachos Daf 27
אמר רבי זירא אמר רבי אסי אמר רבי אלעזר אמר רבי חנינא אמר רב: בצד עמוד זה התפלל רבי ישמעאל ברבי יוסי של שבת בערב שבת
כי אתא עולא אמר: בצד תמרה הוה, ולא בצד עמוד הוה. ולא רבי ישמעאל ברבי יוסי הוה, אלא רבי אלעזר ברבי יוסי הוה, ולא של שבת בערב שבת, הוה אלא של מוצאי שבת בשבת הוה.
Rabbi Zeira said that Rabbi Asi said that Rabbi Elazar said that Rabbi Ḥanina said that Rav said: Alongside this specific pillar before me, Rabbi Yishmael, son of Rabbi Yosei, prayed the Shabbat prayer on the eve of Shabbat before nightfall.
But when Ulla came from Eretz Yisrael to Babylonia, he related a different version of this story. He said that he had heard: This transpired beside a palm tree, not beside a pillar, and it was not Rabbi Yishmael, son of Rabbi Yosei, but it was Rabbi Elazar, son of Rabbi Yosei, and it was not the Shabbat prayer on Shabbat eve before nightfall, rather it was the prayer of the conclusion of Shabbat on Shabbat.
The Bnei Yissaschar in his sefer Magid Taluma writes, that the Tannaim were careful to note the place that a Torah thought was shared, as the association to that place is good for the memory. He continues, and quotes the Zohar, that when one mentions words of Torah a Tzaddik said, in the place it was originally said, the soul of the Tzadik comes to that place, as an impression was made by his words of Torah. Therefore, Ulla was careful to correct the Mesorah and specify the exact place of the Tefilla in question.
We see from here the importance of Mesora and making sure each detail is correct.