yup...clear as mud lol Sounds like it could be a variety of, or combination of unfortunate circumstances. It does ring true though, there's a lot of off smells that creep out at ya when boning, disjointing and seeming out a round, esp a venison round. Another thing that caught my attention was that dark cutters have a higher ph content and thus are more susceptible to faster microbial growth because high ph means low acid and acid is preservative. I worked in a store that sold a lot of cow tenders and often you would have one or two out of a box that had that putrid smell. You got so you could recognize them before you opened them quite often by their really extra dark color. Bottom line is your going to get em and if you can't send em back you're probably screwed.
I agree with Johnny but one question... if it taint meat what is it? hahaha