1x Carbonite-3.34\Carbonite.lua:16226: Invalid reward choice in GetQuestReward([choice])
Carbonite-3.34\Carbonite.lua:16226: in function `GetQuestReward'
Blitz\Blitz.lua:151: in function `?'
Blitz\Blitz.lua:28: in function <Blitz\Blitz.lua:28>
If you disable Blitz, does the error still pop up?
**Edit**
Since both Blitz and Carb have auto quest complete functions, you can also try and disable Carb's if you prefer Blitz. It's the highlighted setting in my screenshot.
With Blitz off and no Carbonite Error, then the issue sounds to be a compatibility problem. Something in Blitz it's interfering with Carb. I would post the error to the Blitz author's BugTracker on their Curseforge site.