Bought from ebay, who do we claim warranty from? ebay seller or Sandisk?
Depends on how long you’ve had it and the eBay seller. If it is faulty or defective, and you’ve only just recieved it, I would contact them. But again, it depends on their return policy.
Otherwise, you can contact SanDisk directly. Note, there are a lot of counterfeit and fake memory cards being sold on eBay. If SanDisk cannot verify its authenticity, they will reject the claim.
in UK, and possible EU, the responsibility rests with the seller for the first twelve months. That is not to say that SanDisk don’t have an obligation to replace, bear in mind though SanDisk will have you post the card back to them at your expense where as the seller will more than likely refund postage.
Some users on XDA have had luck with SanDisk sending users pre-paid UPS labels to return the cards, which in my opinion seems the least they should do if it is a manufacturing fault as seems to be suggested.
My main concern is as SanDisk are keeping quiet on this issue, and when exactly the manufacturing fix was implemented any replacement card may be equally faulty, certainly if my replacement card fails I will be ensuring all future memory card purchases are from a different manufacturer.