This is voodoo - had a couple S9's with same problem. One board (always chain 6) either dead or missing chips on reboot.
This works for me - not sure why?
Turn off all power for a few mins
Reboot with no internet connection
Let it cycle for about 30 mins - it will start up and shut down repeatedly.
Connect internet.
Magic - it runs for about 2 weeks above 13.5TH/s.
Sometimes repeat a couple of times till you get the correct performance - be patient - wait at least 24 hrs till you decide.
If GH/S(ideal) for chain 6 (or any chain) is in the 2k range - repeat immediately. All 3 chains should be above 4k.
Then eventually (after about 2 weeks with 100 x HW errors of the other 2 chains) chain 6 board goes down over a couple of hours in GH/S(ideal) to the 2k region.
Just repeat and it recovers - all good for another couple of weeks.
I'd be very interested to know if it works for you - and if anyone might have an idea why?
NEVER return your miner to Bitmain China (via Hong Kong) on warranty - they take over a month and send somebody else faulty shit miner back - dirty full of mosquitos from Taiwan, not fixed and with same chain 6 problem. Its just a Swaparoo (an Aussie term that CAN mean just keep moving things around, look busy and trying to help - but don't do anything useful). Support goes DEAD eventually if you keep complaining that your WARRANTY replacement has the same problem you started with.
Cheers - usukan
Giving this a shot now on my 14TH/s version. It's had 1 board (chain 6) acting up over the past few days....sometimes it comes online and only detects 12 asic chips and reads a temperature of 15*, sometimes it detects all the asics but outputs 0 hashing power, then sometimes the hashing power output for the whole device shows 0 when in reality it's cranking out the normal amount.
When it does work it seems to only work for a day or two until some of the hashing power starts dropping off, yet the miner status page shows it as hashing at full speed. Usually a reboot or a shutdown temporarily fixes the issue, but this last time it was giving me issues several reboots didn't remedy the problem...the board would come online with all 63 asics detected, but no hash power.
So I'm attempting your fix right now. Shut the unit down through command line then killed the breaker to it, let it sit momentarily while disconnecting the network cable, flipped the breaker back on and am letting it try to connect/reboot itself with no connection. Will be plugging in the network cable shortly and hoping for the best! Will update with my outcome!