I write this edit also because of another thing. With original firmware I always stopped my miner (when needed) with putty and the command "poweroff". Then it stopped mining, but fans kept running so that it cooled down before unplugging.
This doesn't seem to work with BOS. Is there a way to Power Off keeping the fans running? As I have much higher chip temperatures with BOS (around 80 degrees celsius vs 60 with original FW) it just seems wrong unplugging it without cooling it down firs.
Did you try:
Online documentation seems to suggest that poweroff should be in there, are you sure you didn't use any caps? did you try with the full path ie:
/sbin/poweroff?