Post moved to Gameplay.
This has been an issue right from the beginning with a few quests. By far, the easiest way to handle it is to restore to a point before both quests are in the journal, then complete one before activating the other.
Depending on where you are and what you've already done:
- Do all of the Cleaver stuff (arena, casino, etc.) first.
- Be sure to do all the Roche quests/side quests in order. No shortcuts.
Generally, it's beginning the Get Junior stuff then having Gangs trigger in the middle of it that can cause the issue. There were other ways I got around it, but It's been too long since I've played myself. I don't remember the nitty-gritty of what works and what doesn't.