Just got 2 of these, running at 2.5Gh/2.6Gh using osc6_bits=54 with <1% HW errors.
Is there a way to set different osc6_bits for each without having to do it manually in bfgminer
--set-device NFY@Serial_Number_here:osc6_bits=##
try that for each device and see if that works. the S/N is visible for each device in the [M]anage panel of bfgminer
i would also make a note of which S/N is which device with the
dentify command.