Hi guys, probably none of this info will be helpful and has already been said before. I also apologise in advance as I'm new and I like to waffle...
I use my own data SIM to avoid paying for the non-so-cheap rates, so I can't really comment on the intermittent-ness. Although I did use the eSIM briefly when I got the car and performance was poor compared to my EE SIM.
To be fair, those prices are ok-ish if you want to do a European road trip and want data for your WiFi devices!
However, I was interested in how it works considering Audi ship these cars all over the world. As some members probably know, the eSIM is from Cubic Telecom which seems to be a startup of ~100 people.
http://www.cubictelecom.com/Technologies
Cubic have contracts globally with network operators (looks like EE in the UK and Tele2 in Sweden, for instance) and then the eSIM has multiple IMSI numbers so when you go to another country it can change to be a "local SIM". Cubic seem to run their back end for this out of Microsoft's Azure cloud service, so all of the billing and account information and whatnot isn't being sent to a single data centre based far away from the customer - seems sensible!
If I'd have to take a guess as to why the Audi connect services occasionally stop working, I'd say that it's probably an issue with some of Cubic's systems doing the backend connection stuff - or maybe Audi forgot to pay their phone bill that month?
Although, if the replacement unit has fixed some of the issues maybe their embedded SIM is just *****
Either way, it's a bit of a poor show from Audi to not be making customers aware if their 3rd party SIM supplier is having issues; if someone is ringing customer care maybe they can ask if they can look into giving customers an option to subscribe to outage emails from Cubic?
I think I'll only be using the eSIM so I don't burn through my data when I want to do those very very large online map updates...