If you are experiencing liquid trapped inside of the mouthpiece and air flow chamber then it is time to remove this so that you can get back to vaping correctly. In order to remove any vape liquid you have inside the airflow chamber which leads up to the mouthpiece, you will want to fully remove the top of the cartridge and set the glass section aside.
Attached to this mouthpiece you will find the long stem which is the airflow chamber, softly wrap a paper towel around this long stem and blow out any excess liquid that may be trapped inside. Once you blow out any excess liquid, simply put the cartridge back together after giving it a quick wipe down (there will be some liquid that may spray out as you blow through the mouthpiece).
Once this is complete make sure that you have the airflow control valve fully opened which is the small ring just below the mouthpiece, make sure that you see all 3 airflow holes visible. This can also be caused by taking too hard of a pull from the device where it may then act as though it were a straw drawing liquid up towards the mouthpiece.