i believe you are on target about air bubbles cuz the draw is VERY airy. but i didnt think i was injecting much air into the cartos...i am a medical professional and adept at using syringes and it is second nature for me to fill syringes without air...
May i suggest checking for air bubbles in the syringe? My Volcano Magma cartomizers and megacartomizers fill like that; half work perfectly and half have that flavored air thing going on -- then after a while, they normalize and work. My suspicion is air bubbles and I'm checking it out.
Cartomizers I know to work: X-Power 900; pull the cap and drip right onto the fill, works every time. Same thing with e-cig technologies; but those cartomizers are good for maybe three or four fills before the atomizer part is shot.