I have had cursed batches. It was so awful; it was a manufacturer issue, but the product was produced en masse for a fundraiser, and oops...we accidentally shipped a batch that didn't get QC tested here until after I shipped to the client. BIG MISTAKE; I religiously test now. I made good with everyone in the fundraiser, and the mfgr. made good with me, but it still sucked so bad to have to call ahead and say, hey...I just sent you a pile of poop...please return. Humbling? Yes. Humiliating? Yes. My fault? Completely. Even though I got a bad batch of FO, it was still up to me to make sure it all worked, and I (in haste and naivete) didn't test the familiar oil; I had used it for over a year...but this batch of FO was faulty. My supplier was an amazing help; I returned the bad FO to her, upon which she ran extensive testing with similar results to what I found, and took care of that end, but you can't buy back a sullied reputation. It was a MAJOR learning experience. HTH!