December 1, 2021 1:18 PM CET          
          
         
        
          I was using a non-Lego "Foxcm Technic Power Functions Set" battery pack to power my SBrick. 
Every time I tried to update the SBrick's firmware, I got an error. 
This was because the battery pack was powering down before the firmware update had completed its download. 
To solve this, I plugged in a motor to socket A on the battery pack, and plugged the SBrick into Socket D.  Then I used the remote control that came with the battery pack to power the motor connected to Socket A every so often. 
Hope this helps anybody else with the same issue.