I've had the same thing happen. Taste vinigery but is not. So far that taste has not aged out. Lots of suger helps mellow it, but not elimanate it. Its not a wine gone too dry problem. The taste starts early. I had two batches started the same time. Used the same stir spoon in both. Only one went sour, not both. My LHB fella is befuddeled. Suggestions to fixing it would be great!