I opened it up and the connection from the PCB to the motor was fried. As I said in my initial post, everything was standard configuration with the exception of the change to 3S lipo. The stock servo is working fine

I have another 255 on the way, however I am going to wait until I get the rest of my upgrades (mamba micro pro combo and a few other bits) before installing it

Not really sure what the issue was, but will switch to savox if I have any issues with the 2nd servo. Bit disappointed, but not sure yet whether it was something wrong with my setup or if the servo just failed? Is it possibly issue with analog vs digital?