I have had half of my M3's (1 of 2) go bad. Dead hash board.  After initiating warranty claim on their website, you're directed to a Telegram channel for support via TeamViewer.  The Florida address seems useless.  I asked about sending to FL address, but was directed to ship failed board to China (confusing address has to be 100% correct or they claim to not know where it went).  They eventually found it and sent a replacement - turnaround time is about a month.

They could really improve their reputation by getting their Florida address operational for North American support.
 Even if their hash boards  have a high failure rate, if they can get the turnaround time closer to a week instead of a month it'd still be worth it.