Green Cabbage - Raw product producing strong odor

In the past two months we have had two separate shipments of prep cabbage that have put of a strong irritating odor (similar to irritation from onion) during the processing phase of dicing and shredding. We first concluded that the vendor does use a chlorine spray on the product after harvest, mixed with our chlorination process, the combination of the two was causing the irritant. Since the issue has now become repetitive, I was wondering if anyone had any other input as to what could be causing the odor? The raw green cabbage shows no signs of decay or mold, the shipment and storage temps have been checked for possible deviations. The product is stored with other non-ethylene producing leafy greens and similar products (No Allergens Stored). We have sent samples for lab processing, but was wondering if anybody has previously encountered a similar issue and what the results were. Thanks for any help provided.

Not really my field but  what about  checking  for a pesticide  residue?

Have you asked the supplier if they have changed anything?

I would most certainly look into what TopKat said about pesticides .  Check that out.