Basic questions in the Tosheva

The Oral Torah was passed down orally until then and it was forbidden to write it down. I assume that all of these files are compilations that collected the reliable sources that were ruled on by the halakhah. But there were several editors and they had different opinions (Rabbi Chiya, Rabbi Ushaya, Rabbi and more). Some of the sources may not have reached them at all. When they say that every baraita that is not found but Rabbi Chiya and Rabbi Oshaya is distorted, they mean to say that it is difficult to trust baraita that was not included in those collections. This does not mean that all of them are distorted, but that there is a greater concern there. Therefore, if there is a difficulty for which a reasonable solution cannot be found or there is a contradiction with a source that is found within, then the baraita should be rejected and not the other source. But still, when there is such a baraita, it is part of the oral tradition that has come down to us and has not been written down, and therefore it has weight. Hence, they try to check whether it is nevertheless reliable and correct.