Fridges running on gas

We have just taken delivery of a new caravan with a Dometic fridge freezer. Running the fridge on mains it performs perfectly.  However, when running on gas there is quite a strong smell of burning.  As the vent for the fridge is within the awning, it makes the awning very unpleasant and also the smell feeds through the part open windows into the caravan. Is this normal and just because it is new and not been "burnt through" as a new fridge?? Comments would be gratefully received.  Thanks