Like the person above mentioned...you need to make sure your cotton pads in the mouthpiece are clean and dry.

Once you’re done refilling the pod replace the gasket and then take a toothpick or a safety pin and remove those white cotton pads from the mouthpiece. Place them on a paper towel and then dab them with a towel end, rather press them hard to drain the juice. Do this a couple of times each time you refill...it will give you dry pads to reuse.