It is not leaky, it's flooded.
Overfilling / improper filling is e main culprit if juice leaks out e bottom airhole. A quick tip for refills w/o wearing down orings on e caps is to push e connector / threaded end of e carto slowly into e tank. Tilt e end slightly and use a needle-tip btl to drip liquid in e gap btwn carto and tank. Let e liquid slide down e sides and clean up wen almost 3/4 way full. Push e carto back up via pushing on e drip tip end whilst holding e caps securely and you should be good. There are plenty of ways for refills but this worked for me when I first started using e dc tanks.
A question for u, how long hv u been using e carto..?
Most cartos hv a lifespan of ard 3-4 refills (not necessarily so, but is advertised largely) but u can get carto life of up to 2 weeks with reliable performance. Beyond that, e carto wld give poor vapour production and they mite not hv e capacity to hold liquids as well as wen wen they're brand new. Flooding is one of e signs that yr carto is as good as gone, unless of course, it is brand new and that wld bring it back to e first option, overfilling / incorrect method of refilling.