Karcher RCV5 Robot Vacuum Stopped Working, Refused Replacement Due to Lost Receipt

We bought the Karcher RCV5 robot vacuum last year, and it worked fine for a few months. However, it soon stopped vacuuming even though it was running. We took it to the service center, and after a few weeks, they decided it needed to be replaced. But since we misplaced the receipt, they refused to give us a replacement, leaving us with a defective product. This has caused us a lot of frustration, and if I had known this would happen, I would never have bought from this brand. Karcher, you need to improve your customer service and offer solutions for cases like this. We feel completely let down by this experience!