Cool thread line. You can definitely get rid of the pro- tank gurgling - dependant upon the cause. Without narrowing down the cause by trying different things - you can change the coil and that should fix most issues. The only thing that I have found that causes leaking/ gurgling without reprieve is heat - I live in Phoenix. Every time I go from inside (air conditioning) to outside (summertime 100 degrees +), within 5 minutes - no matter what tank I have(except an genny style RBA) it will start gurgling / leaking unless I turn it upside down for a while. Has to do with pressure.
I would suspect that in your case, the wick has burnt down to the point it lets to much
juice in, or you have the same issue as I do heat change. Altitude (trips to California) does the exact same thing. In my experience, the Protank has less of these issues than most. The vivi has a good taste - I do use mine a lest once a day - but you have to "chase the
juice" (tilt more as the level drop) or you get dry hits.
One last thing - just try to remember one thing - we are using a device that holds juice and has to have a least two holes in it. Only drippers have no leaking issues when used right.
Hope some of my rambling helps.