What I guess may be the first hashboard has a bad heatsink bad adhesive or solder on that chip same on the 3rd hashboard. However, would you mind try replacing the PSU I see weird under Vo it shows 0 so it might be your PSU giving a false signal?
Thanks for your help. Where do you see "weird under V0" ? As the avalon is still under waranty, with log problem I coul'd ask for a new one