Your Ribena probably had potassium sorbate in it, which inhibited yeast
reproduction.. Then since there is little yeast to ferment and fight off
the nasties, something else must have gotten in there and took over. Not
surprising, really.

LG

Hi
I was racking a gallon of Ribena, (blackcurrant cordial) type wine today and
had a quick taste before I started. There's a strong fusty/musty after
taste. Also after 4 weeks of bubbling it is still extremely sweet,
confirmed by the hydrometer. Sorry can't remember the reading but the
hydrometer was halfway out of the liquid.

I'm guessing the alcohol content has not risen that high and as such
spoiling bacteria have got in, hence the after taste.

Any point continuing with it or should I flush it and start again?

tia