Request Operational Record: Request in-depth information about the miner’s operational history, like use length, routine maintenance documents, and any repairs or replacements. You may also prefer to return the faulty machines to Canaan. With this issue, Consumers pay out inbound shipping and delivery and we can pay the return transport. https://refurbished-antminer-z1577415.timeblog.net/74865673/understanding-antminer-z15-profitability