The business I work with sells millions a year on eBay and buys an equal amount. eBay is around 14% of our sales and our purchases each year. I have seen it all, the stories I could tell. Anyway if it is too good to be true it usually is, so just approach with caution. We experience on average about a 30% non conformity rate on products coming in from eBay. What happened to you would classify as non conformity, same for us many times we can work it out, that cost extra labor though.I've found eBay pretty safe. That's because there is a buyer guarantee. If a seller advertises a 30-day return policy, I've found it works every time. I've even had 2 products that a bulk seller got wrong in his ad mostly likely since he bought out a hifi store that went out of business and didn't know what he had. I had lots of leverage where I could have gotten my money back, but opted to negotiate a better deal both times. I find eBay to be a good marketplace if you know what you are buying. If you don't know what you are buying, you can easily get the wrong product.
We are not buying consumer products.
Hard not to caution based on what I have lived.