I'm glad to hear it!
I see I forgot to post a final update on this case here, my apologies;
The flavour inconsistently was determined to be caused by the natural flavouring. Not the cacao powder, but the other natural flavourings. The affected batch was produced with a new lot of natural flavouring, which was different from normal. The issue was purely a flavour difference, not anything harmful. We've obviously removed this abnormal flavouring, and produced a replacement batch with a new, good, natural flavouring.
We've retracted several hundred bags of the affected batch from our warehouse, and replaced it with a new good batch.
A new protocol has been implemented to obviate similar events occurring in the future.