During the task you take Uncle, Tilly and Karen into town where they fall into trouble, resulting in a rescue mission. The bug appears if you die or fail the task and choose “Retry Checkpoint” instead of restarting the mission from the beginning.
Red Dead Redemption 2’s individual storylines are worth indulging, especially as John Marston’s relationship with Abigail is what inspires the basis of Red Dead Redemption, the game’s predecessor.
Considering how easy it is to trigger the bug, it’s more than likely that a large selection of players have missed out on the side quests. Reddit users have failed to find a way to solve it, and developers Rockstar made no reference to an upcoming patch in their reply to Reddit’s r/xbone, which said:
“Thank you for contacting Rockstar Support,
We understand your concern regarding the missing storyline characters in Red Dead Redemption 2 Story Mode. Please be informed that, if the missions “Polite Society” and “Valentine Style” are failed, restart the mission instead of using the “Retry Checkpoint” option. If you have already completed the mission after using the “Retry Checkpoint” option, they will not be present until the start of Chapter 4. We hope you understand.”