It depends what you're referring to... In your description it sounds like the MIB unit is freezing. This often happens when it's cold (weirdly) although I have known it to happen on warm days too! Usually fixes with engine restart, or reset the unit by holding power for 10 secs. If it's just your DAB with issues, it should generally be top quality, but I lose signal when driving past tall buildings in the city centre, just the way DAB is broadcasted.
There has recently been an MIB update released which people have said does help any freezing issues so might be worth visiting your dealer.