GM
I run my s9’s at 700-900w and still get pretty close to peak performance with Braiins.
Did you try flashing the OS?
Discussion
It will be my step tonight, for now I down tuned it yo 100w/ board as I am not home
You can leave it as is. Whatever watt target for braiins assumes its spread over 3 boards and the ~75w overhead for control board. So if it was 975w, it would be roughly 300w to each functioning board and that needed for control (675/975). With one hashboard down vs the controlboard, it'll slightly raise your watts/Th.
A physical consideration is to ensure the remaining good boards are not in the hot board lane, allowing you to eek out a bit more hash in the other lanes with higher temp threshold. Remove bad board or unplug its power.