On Nov 2012, I escalated this issue with the dealer support team, after tons of back-and-forth emails, the dealer support team confirmed the issue. Last Thursday, Feb 15, I got from support team the Teltonika will fix the problem at the end of March. It is not really fast.
I am not sure if it is a 2G network issue. I have customers with 3G and 4G networks, and they have the problem as well. If it is a network issue, how you can explain that you can upload configuration and firmware by FOTA? Could you test these kinds of functions on your devices? I know it is an error from Teltonika because FOTA works fine.
Let me know how your tests go
Cheers