Ok I'll try downgrading. Do you know which firmware corresponds to S9V2.23? The filesystem is dated to Jul 21. Or is there a way to dump it directly?

I have two 13.5TH S9s from the November 2017 batch, lets call them worker1 and worker2.

Worker1 is running firmware version S9_V2.51: it averages 13.63TH, temps around 80, will occasionally switch to a lower priority pool (when worker2 has no trouble reaching priority 0), and has its chips clocked to an average of 626.74.

Worker2 is running firmware version S9V2.23: averages 13.92TH, temps around 75, and has its chips clocked to an average of 641.25.

Worker2 is performing faster, cooler, and running an older firmware version than worker1. Should I flash worker1 with S9V2.23? Or just accept this as random hardware variance.