I had this happen overnight as well on one of mine. Temp on mine is 42 & 43 and it is sitting in an aircon server room.
Unit is definitely hashing away on 400 setting (202Gh/s) and pool reporting continual hashing data, so xxxx must be bogus in some way, or at least does not prove unit has stopped.
I will join this club.
Woke this morning to:
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
Shut it down and let it sit for 5 minutes.
Now back to:
oooooooo oooooooo oooooooo oooooooo
oooooooo oooooooo oooooooo oooooooo
(at least for the moment...)
S1 had been running for >4 days constant.