Amazon has a policy of binning items with the same UPC together, regardless of the source. What this means is if you buy a valid product and any vendor who is part of their warehouse storage system sells counterfeits, then there is a chance of you getting a counterfeit part, regardless of who you buy from. This reduces the number of locations required for a given item. It just requires that you trust your vendors to not counterfeit. If they were kept separate you could easily see who is selling counterfeits, but it would require more space.

So Amazon has traded the ability to sell parts from verifiable vendors for short-term profits. At this point in the game, your best assumption is if there is any knock-off company selling the product you wish to buy you have no way of knowing it it's legitimate or counterfeit. This is currently diluting their brand and will ultimately impact their sales, if not their profits.

Well the easiest solution is to go back to having Amazon be the seller of products on Amazon, but we all one that ship sailed.

But if the problem is shared bin storage, the solution isn't free, but it's also not as expensive as lots of buyer confidence:

Tag every item with a QR code indicating its source when it comes into the distribution center. Use that code to identify the bad actors when there are returns and ban them.

"But what about products not shipped by Amazon?"

In that case, you know who sold and shipped the product, and if they can't get their shit together they shouldn't be allowed to work with Amazon.

It's not hard to do it, its hard to do it and make the same amount of money...