I sometimes buy specialized tools and equipment from Amazon due to the convenience of Amazon's great catalog and suggestion system, it can be quite useful.
However, sometimes I receive items that are clearly B-stock, returns, mislabeled defective, improperly packaged, etc from these third party sellers who "win the buy box".
The subtle difference between useful and completely useless is really hard to demonstrate to someone who is not familiar with the usage and normal appearance of these products.
When I have a problem with some of these specialized industrial products I often cannot simply return them for service or warranty to the reseller, I am required to return them to the authorized reseller (Amazon is often one of these) for warranty service.
The problem with this is that the manufacturer often only warranties their product when sold from their authorized reseller. Even though Amazon may be an official reseller affiliate, the third party reseller that I purchased it from (again, FBA, but sold by GUYA JICKSV LLC) is not on this list!
In order to get the warranty service I now have to go to the manufacturer, who is wary of theft, counterfeit, returns, and a really surprising number of times I discover that there is a part missing or duplicate parts, and this renders the warranty void.
Dealing with the manufacturers in these situations is really annoying and often fruitless. To them its just one unit and they do industrial sales volume, but to me it is several hundred dollars and days of hassle. This costs me much more money than the cost of replacing the thing.
I am now very wary of buying certain types of products from Amazon, as they often appear to be sold by Amazon, but is actually not sold by Amazon, but only technically sold by amazon because of this buy box behavior.
Its is incredibly opaque, error prone, and nobody cares except me and my customers (with whom I sure do have a relationship, unlike the Amazon seller does with me.) As a result, I have reduced my purchasing from Amazon. Cest la vie.