Butter is diacetyl. Yeast can eat it, so fortunately it ages out. Typically this will take 2-3 weeks in beer. I'm not sure how long in a ginger bug but my guess is similar timeframe. So just be patient, and give the culture time to eat it. Good luck!
Hey so I did a test run myself with some instant coffee and I managed to get it to carbonate.
Here are my steps,
Step 0: Boil water and let cool or used distilled water
Step 1: Mix instant coffee and water into fermenting vessel, about one tablespoon of instant coffee per cup of water
Step 2: Allow the beverage to ferment for at least 3 days
Step 3: ...