Considering that you "bought" your venison I assume that it was from a deer farm as it is illegal to sell wild venison. The cause of you problem could be from:
     1) It is ground straight with no added pork and/or beef.
     2) The meat was allowed to age to long and started to spoil prior to grinding.
     3) The meat was not properly wrapped and had moisture loss and/or picked up smells and/or tastes from other items in the freezer.
     4) The time between thawing and cooking was to long and spoilage started.
    5) You have not eaten venison frequently and may not be used to the smell / taste compared to beef and pork.

    Try mixing it with ground pork and ground beef.

Dave