When doing the quest "Bye Bye Love" Joana (and sometimes Carlitos) vanish from the game.

Repro steps:

1. Take the quest "Bye Bye Love"
2. Get to varying stages of the quest before the escort Joana part.
3. Do the quest "How Little We Know"
4. Kill Big Sal and Nero.
5. Observe Joana missing from Gomorrah Courtyard. The quest marker is there but the NPC does not exist.

Other information:

Sometimes after killing Big Sal and Nero you will instead fail the quest "Bye Bye Love" it seems to be determined by what stage you are at in the quest.
Several users have also reported that Carlitos goes missing from Vault 21 as well.

In my game the quest is broken. Carlitos is not in the diner or the Vault hotel at all. Anybody knows how to fix this?