Hi.
It isn't really something wrong. It's more a characteristic of these clearo tanks. Did you clean the coils well? It could be a sign of gunked coils and wicks. Scout around for the other 15 threads on cleaning and dry burning. No need to rehash it here.
However, the leak/gurgle does happen at times. (and more often with non halo juices, for some reason)
Assuming all is clean and assembled, take a tissue at the bottom of the tank and blow the tube clear. Yes, you are blowing the other way. Sometimes I'll go the other way, put the whole bottom of the tank in my mouth, or cover the 2 air ports, and blow the tube clear into the tip, then swap the tip with rolled tissue or q-tip. I also dry the bat top, sometimes with a thin drinking straw and tissue to get into the "moat".
I immediately take a few hits to see how I did.
And this does happen just after refilling. When screwing on the top, it might compress the contents a bit, and this will flow into the center tube. I mean, where else could it go? It has to equalize the pressures. And we are talking about just a few drops.
So, blow, wipe, repeat if necessary, vape.
Hey!!!
Welcome, JollyGiant!!