I also have this problem. I can 'stop/cancel/end guidance/navigation' using either the iDrive or Voice commands like normal like everyone else, UNLESS I have actually arrived at the destination and the large dot has appeared on the dash. Using iDrive buttons the checkmark disappears then reappears on its own, and using voice commands, the Voice tells me that guidance is off but it is still on the dash and won't turn off. I have often told the 'Voice' that she is incorrect in my nicest tone.
My work around has been to select a stored destination (like my home), 'start guidance' and then 'Stop guidance' using the Voice. Then everything on the dash shuts off.
Of course, I could just shut the car off but then the 'voice' would win.