Viomi Defective Upright Vacuum Cleaner

I purchased my Viomi vertical vacuum cleaner 1.5 years ago, and it has been returned to me three times for the same problem during that time. When we send it to the service, they say it's because of user error, but when we involve the insurance, they say there's no user error and wonder why we sent it to them. Whatever way you look at it, it's a disaster. Furthermore, they return it, claiming the product has been repaired as if mocking the situation, despite the fact that the problem persists. It was in repair for 44 days during the last service. Teknosa contacted me and offered a refund, which almost sounds like a joke. Can you still buy the same product for the same price 1.5 years later? Shouldn't a large corporation, such as Viomi, provide a new one or their top model as a replacement?