What atomiser are you using? I've found that with the 510 atomisers and found that when you take off the tip (the part of the plastic mouthpiece with the hole) by very gently biting down on the plastic 1/2cm from the top, the tip comes off, looking inside you'll see that there's another plastic cover with only a small hole, this is where excess liquid can acumulate and I used to sponge out the excess with a tissue when this happened. I've since discovered that by pressing down firmly on one edge with a watchmakers screwdriver, that disc of plastic will come off, which should solve this problem.
Hope this helps
All the best
Chris