Trustee of a contract

And if the Gemara said that he was not trustworthy, then what would happen? The halacha should be that they divide it (or another solution, I don't know when they say anything). If at this point the seller were to decide to ignore the halacha and choose one of them and sell to him again, would they tell him who broke the law and that maybe he chose the wrong buyer? If not, then it makes no difference whether he is trustworthy or not, but it is difficult to say that they would tell him that he is trustworthy.
If I understood Rashi correctly in Kiddushin, he mentions who broke the law in this matter, which we assume that the seller remembers who he sold to because he is afraid of who broke the law, but he does not say that he is trustworthy, and therefore he was not told who broke the law.
And even if from the Torah, one buys from a rabbi, one does not buy from a rabbi, then what good does it do?

I didn't understand anything.

1) It doesn't matter whether the seller is trustworthy or not. Even if he is not trustworthy, he can sell to whomever he wants and (it seems to me) they won't tell him who broke the law, lest he break his word and sell to the wrong person.
2) I understood that Rashi in the Kiddushin mentions who broke the law to explain how we know that the person remembers who he sold to. Rashi explains that because the person is afraid of who broke the law, he remembers who he sold to. Rashi did not say that if the seller was not trustworthy, they would tell him who broke the law.
3) The rabbis buy from the Torah, but not from the rabbis. So why is the seller's loyalty needed if the sale has not yet taken place (from the rabbis) and they will not make him who broke the law?

1. You make assumptions and make questions difficult. Don't assume and don't make questions difficult.
2. Rashi mentions the one who transgressed to say that when the buyer is in his hand, he is precise so as not to transgress the one who transgressed. Exactly what I wrote. If he didn't remember and therefore was not faithful, the one who transgressed would be on him. Otherwise, what is he afraid of?
3. This can be a discussion on the Torah level even if it is not relevant to the Drabnan level.
Of course, it can also be a situmta to buy with money, and also with land where money is useful, and the like.