Yes I did it myself in July as I have the last two firmware updates. BUT the exact procedure needs to be followed which includes pressing the brake (auto) or clutch (manual) every 20 minutes to ensure the headunit did not fall asleep. Also did not have a battery charger connected which is another risk unless you have a relatively new, fully charged and reliable battery. And don't restart the engine in between the two installation files.
OK, to recap, you upgraded the CMU yourself to 545 in July and the Maintenance menu was the same as before, later on you had the ECU upgraded and you noticed the new Maintenance menu, is that correct?
Just tell your dealer that the display randomly goes to a black screen whilst navigating occasionally, they should do something then
This is exactly what is happening sometimes, the screen goes black and the message Loading Navigation with the rolling circle appears, but it seems more frequent with the real-time traffic information enabled though.
Cheers
Eddy