i have had the same problem too! only when my cart gets juiced up then you lose vapor production.
in a matter of fact you need to pop two caps, yes two. first one is the top one of course then you will see a flat bit with a hole in it use a paper clip to pull that one out and man it is sweet for air flow and no bits flying in to your mouth.
also rinse the cart out to wash out any residing juices (not the cart material but the plastic bits)