In the meantime people just keep on sending Titans in for fixing. Latest repairs included a board that had a burned plug (fixed, all dies working) and a totally dead board with a short on pin 8.
Which usually means a die blew up, but in a way that you can isolate it from the rest of the board. Normally it takes awhile to figure out which die is bad, but in this case the scorch marks under the board narrowed down the options a bit. It's back to hashing on 3 dies, so a pretty good success.
Brings up a point: If your Titan cube is running 48C or higher the heat sink is loose, stop mining and fix this. Normally the heat sink compound KNC used was stuff that dried rock solid; if the cube gets jarred the compound literally crasks like ceramic and it won't conduct heat. So you have to remove the sink, clean off all the old compound with a plastic spoon and isopropyl alcohol on a paper towel, then when totally clean put some new compound on (I like the Artic Cool stuff myself) on the die and on the heat sink bottom (clean that too first) then put it back on and tighten the bolts down.
Then I like to do a little wiggle of the heat sink to see if it can rotate a bit. If it moves even a little on the die it's not snug enough; you can't torque it down further but you can buy 3 very small washers, put them on each bolt, then carefully snug them down until it won't move with some torque force on the sink. That's tight enough.
Another think I like to do is take one of those rubber things (there are two under the board) and move it to between the top two bolts to support the front of the die. Otherwise if you tighten too far you get a taco board and not good heat sink contact.
Anyway, back to fixing things.