Brian, one would think that you're lucky enough to have some good south american vineyards near by. They're really starting to make a statement. Perhaps you can source from someone local? Either case, the unpleasant aromas shouldn't be happening early on. The smell should be fruity and yeasty like bread. It makes me wonder if perhaps your equipment has been contaminated with something, or maybe your juice goes bad in transport. Does the juice smell like grape juice when you pitch? If the juice smells fine when you open it then I would think it's your equipment and try new buckets and whatnot. I once contracted bretts in my 1 gallon equipment and it gave everything I put in it a distinct vomit sourness. After much research I discovered that bretts can't be sanitized or bleached or boiled away, it creates a skin-like layer on your surfaces and hides out under there, waiting for optimal temps and moisture (aka your wine) to come out and thrive. Horrid, nasty thing, that bretts. Not bad in beer, some of them use it on purpose, but off putting for wine. Anyway, I hope you can solve the mystery, that would be very frustrating.