Our Gemara on Amud Beis refers to an Amora who they considered to have an unreliable memory and confused the Mishnayos and beraisos he quoted. It is interesting that he was regarded with some degree of deference as a sage, despite this major shortcoming. There is no explanation in the commentaries aside from brief statements by Rashi and Shita Mekubetzes who seem to confirm that he was a respected Sage who confused his teachings, and was oddly tolerated despite it.
His name itself offers us a possible clue but without any definitive proof. The name, ada bar uchami, means “ada the son of the black (or dark) one (uchami)”. Often, people were given nicknames based on appearance when born as well as life incidents. There is an interesting story in Gemara Ta’anis (22b) about a person who worked for the secular government and wore black shoes (uchami) which was a gentile custom in that area. He dressed that way in order to be incognito and was able to pass along vital information about various pending evil decrees, as well as stealthily save Jewish prisoners. Eliyahu Hanavi told Rabbi Beroka that this person merited a place in the world to come, despite his appearance and not wearing tzitzis.
Was this person Ada’s father? Unknown. What was Ada’s merit that despite confusing teachings he was still accepted by the Sages? Unknown. Is it possible that being the “uchami”’s son was his merit, since he was moser nefesh on behalf of Jewish welfare, maybe, but no conclusive proof for any of these conjectures.
Translations Courtesy of Sefaria, (except when, sometimes, I disagree with the translation .)