This is utterly unacceptable and they cannot simply say they cannot do anymore. It strikes me that the whole navigation unit needs replacing or the gps sensors but I am no technician. Frankly I would now escalate this via the dealer manager and if he does not respond to Mercedes UK.
It is a real shame this is happening at the time of the chip shortage as it may introduce reluctance to seek the parts but I am unaware that the basic navigation system is in shortage.
They simply cannot say “oh we do not know what to do“ they do it is to contact mercedes themselves who will know how to fix it even if it means a new head unit. There is something wrong with the car that can be and should be fixed. I would now start rattling some cages and certainly would not accept the position.
I have had 4 new mercedes and the navigation systems have always been excellent. Disgraceful service but that does seem to be a feature of so many UK garages ( I assume UK from your country of registration). I always had good service when I lived in the UK though my exoerience with mercedes was for a very short period as I left the UK soon after buying the car but what exchanges I had with them were as good as the Ford, VW and Audi garages I had dealt with.
Good luck and do not let them fob you off.
