its possible that your atty head is not screwed in tightly enough. that happened to me. i think it was from unscrewing the top cap, which in turn, could loosen the atty head slightly enough to allow juice to seep in the center tube. this could also be due to your silicone stopper not making a perfect seal withthe top cap.
unscrew the top cap, wipe the excess liquid from the inside. wipe the excess liquid from the top of the silicone cap. remove the silicone cap and make sure your atty head is screwed in tightly enough. i use my thumbnail for this, some folks use other tool such a a paperclip. dont make it too tight, just snug enough. then blow out the center tube and dry off the 510 connector.
also, dry off the area inside the top cap that become visible when you remove the drip tip. i get backwash in there sometimes. that could also be a source of your gurgle. also, theis should be a regular place for you to wipe clean. the backwash can roll back down into the tank, ans im pretty sure vaping backwash isnt too high on anybodys list of things to do.
and finaly, dont overfill your tank. i do 3ml as a max. 2.8 preferrably.