Amazon doesn't have a method to handle issues related to UPCs. Every ASIN that exists is assigned a product ID. Whether that product ID is a UPC/GTIN, GCID (Not even sure if this is a thing anymore), MPN (brand registered/UPC Exempt), etc. In the earlier days of the 3rd party marketplace new sellers were easily granted UPC exemptions en masse and could create any listing. The site filled up with duplicates and fake listings. So Amazon decided that a UPC was required for all new items, and UPC exemptions can be applied for on a per item basis. Then, Amazon decided that all CURRENT listings required a UPC and everyone had to provide one for their listings. The UPCs however did NOT need to be GS1 registered. So disreputable companies would sell UPC packages to Amazon sellers for cheap that were randomly generated. That and sellers would just make up a UPC number because they don't have the real one, which leads us to where we are today.

Hijacking listings has become EASIER, because UPC is king. Everything that is the ASIN, the reviews, the product data, images, weights, sales history...all of it. It all revolved around that UPC, and if someone can take ownership of that UPC, they own the item entirely. I don't believe that any department of Amazon has the tools or permission (per company policy) to fix these things. I'll give you an example:

I am trying to list a product with the manufacturer's UPC code. It's a facility maintenance chemical that comes in a 5 gallon pail. The UPC is GS1 registered under that manufacturer's name. The manufacturer's website shows an image of the product, and the page lists the UPC. I took pictures of the product showing the manufacturer's name and UPC code in the same picture. When I try listing that product, it comes up with a remote controlled helicopter listing. I can't change any of the information including the brand name and images. I spoke to Seller Support who told me to speak to the catalog team. I spoke to the catalog team who told me to speak to Brand Registry support. I spoke to Brand Registry support who told me to speak to Seller Support. I posted on the forums, Mods can't help. There is literally no one who can fix this problem. The furthest I got was "Only the brand owner can change the listing." There is no brand owner for this manufacturer's product on Amazon. The manufacturer doesn't sell directly on Amazon,and there are around 10 of us authorized distributors selling the product line.

Until Amazon takes a step back and examines how the catalog works and creates an actionable policy for seller support, these problems will never be fixed and people will continue to hijack listings.