Then my guess is it's too thick for cartos. I use 20% VG or less in standard stuffing cartos. 30% works but I feel the drag/wicking suffers a bit. I won't go thicker on standard resistance cartos (which are all you can use on slim ecigs).
tanks/reservoir cartos like 20-30% OK and maybe some thinner 50/50's
Alternately - if you are using thin liquid then maybe the carto is improperly filled/settled. Or maybe you are using CE2 cartos and the wicks are pinched. I don't know. Not Enough Info on what you are using. What is your PG/VG, what ohms atomizer, what type/ohms carto?