When playing through the DLC you will get the quest "The Quick and Quickerer" from a woman in Vestige that looks like an undertaker. It seems like if you leave the town during the first couple of stages of this quest it will hard lock and you will not be able to complete it in any way.

The best way to avoid this issue altogether, is to grab the quest and finish it, before leaving Vestige.

If you made the mistake to travel out of vestige during the quest and locked it up, there is no easy way to fix it, as the your savegame itself will be hard-locked. In order to resolve the issue you will need to edit your save to delete the quest altogether and pick it up again.

1. In order to delete the quest from your savegame you need to install the CLI Save editor for Borderlands 3[github.com] by
   following the instructions on the page.
   
2. You have to locate your save files and identify the save file with the broken quest. The default
   location for save files is
   
   C:\users\<USER>\Documents\My Games\Borderlands 3\Saved\SaveGames\<STEAM_ID>
   In case you have multiple save files and need to identify the broken one:
   
   1. move all files except profile.sav out of the SaveGames folder
      
   2. move the files back into the SaveGames folder one by one and check which character they belong to by choosing "Switch Character" in the main menu
      
   3. note the filename of the broken savegame
      
3. Open a powershell or cmd and run the following commands
   
   cd C:\users\<USER>\Documents\My Games\Borderlands 3\Saved\SaveGames\<STEAM_ID> // THEN // if you are on NVHM bl3-save-edit old.sav new.sav --delete-pt1-mission /Game/PatchDLC/Geranium/Missions/Side/Mission_Dueling.Mission_Dueling_C // if you are on TVHM bl3-save-edit old.sav new.sav --delete-pt2-mission /Game/PatchDLC/Geranium/Missions/Side/Mission_Dueling.Mission_Dueling_C
   You can choose to use the same filename for old.sav and new.sav to override the save file. WARNING: Do this on your own risk. I recommend creating a backup of your savegame by not overriding it.
   
4. Load the new savegame to verify you can pick up the quest again.

I am aware that the CLI editor may not be for everyone, but I tried my best to create an accessible step-by-step guide for everyone to follow. I recently discovered there is a GUI based Save Editor[github.com] in the works, however it currently does not support deleting quests from your journal. I'll keep an eye on that and update this guide if the functionality becomes available at some point.