Hello,
I too have had the SOS failure, only 3 times in abour 3K miles. On the 2nd failure I lost all the functions from the entertainment unit & sat nav put me miles away from where I was showing I was travelling through fields :shock: . After the 2nd failure my local VW dealer had a look & adjusted some parameters, since then 1 SOS failure (taken photo as proof, as not rebooked in) with entertainment unit fully functionable inc sat nav. I wait to see how it behaves.
I did find a YouTube video from an Audi owner who found a "reset" I'll try & find the link & post here. When the SOS failed he pressed & held the SOS button, after about 60 seconds the sustem started to connect to the SOS people, he then cancelled the call & the system reset back to normal. If mine fails again I shall give it a try.