Navi system in the tunnel!

Hello, I bought a TomTom Go 700 because the leasing company where my car is leased sold to me at a preferential price. Except for the unsettled assembly the thing works amazingly well! One thing, however, came to me angry. I had a failure in a tunnel in Prague because of lack of satellite contact, and I was able to get past an exit, because like the devil the exit was so close after the tunnel end that the system did not get fast enough connection. Now a question to the users of the RTI system: I heard once that manufacturer-specific systems are connected to the Tacho, and so this problem only appears after a long journey without satellite contact. Would be grateful here for clarification. Greetings from Prague.