On some systems ( Shimano e8000?) you get a fault if you start the bike with your foot on the pedal..........suggesting the reading the controller ( TCU in this case) from the torque sensor on start up needs to be zero. That does not seem to be the case with Brose so I wonder if Spesh have set the software to accept a range from Zero to a minimal positive torque giving it a range of acceptable stationary settings..........and that range is what the fault code is referring to. So as @Bearing Man has indicated I wonder if somehow during your rebuild the torque sensor is either not sending any signal or due to misplacement is sending too large a torque setting signal.