If your having issues with D3 randomly stoppin g mining there is a firmware fix for that.
If boards are dieing you will need to send them back to bitmain.
We have 16 D3's from Batch 2 and 8 have suffered this issue. One of them has now lost two boards.
yap! the same to me, 2 boards off, than another is going faulty last few days and I am worried that will go 2 boards off equally

You have send them back than to bitmain than? how long does it take to get the new one from them?