Thanks for the article. Really helped to boost to 28.3 Mh/s in single mode (at 74 degrees C, 95 watt)
Not getting any hash errors.
I wonder if you have sufficient power/volttage on the cards.
Do you think that you have sufficient PSU?
I remember similar issues with DDRAM (depending on sequence, placement) - I was "losing" RAM till I found that stronger PSU solved it
NB: going to install more GPU, will report back with my findings (so far running just one)
Cheers