I did as you said. I deleted the game and the walkthroug mod and reinstalled the game. I restarted the game (at cuckolded route), followed the walkthrough (pdf), step by step, and ... the result was the same as I have said. Andrea invite MC to share Mary as they havd dealed (???). This dialogue is a nonsense, because the deal was made between Andrea and Justin, not with MC. I know that it's not right according to your story, so I ask you again: Do you know if this has happening with others users, or only with me? Best regards.
P.S.: If this specifc scene will have no impact in the future, I don't care at all. Tks.