I've had MHD for a couple weeks now on my 2013 335i xDrive n55 and have had some failed writes before, but always recovered them after charging my battery the whole night. I went to flash to a new stage once but noticed my charger didn't have a proper connection and wasn't charging my car. After this fail I've tried charging my battery for a couple days, getting a new battery, and a new charger. With trying all of these things and following recommendations like unplugging the fuel pump fuse and putting the seat belts in, I still have errors. I'm thinking about possibly bringing it to a BMW dealer or finding someone who could recode my electronics near by but I've heard this is unnecessary. Not sure what to do anymore I'm hoping to find if anyone has been in this situation before and how they solved it. I've tried flashing to stock and different maps all with the same result.
Here is a video of me going through the steps: