Quick question, what's the average uptime on your D9's? I'm getting around 18 hours - 2 days between resets, not sure if it is normal behaviour.
Same is happening for me! It automatically restarts, I think that is the issue with my A4+'s too. It keeps restarting all of a sudden. For D9, one of my boards stopped working automatically as well. Had to send it to China for warranty. Waiting to hear from them.
One of my hashboards also stopped working. Did you talk to support? I will have to check tomorrow, maybe its just some problem with a contact or so.
What about customs, if you return a unit for warranty?