I've got a zlide tank that I'm having some problems with. Seems to be leaking liquid out of the fill port section when closed. After filling and closing up the tank and vaping for a while I find there is liquid finding it's way out and leaking out and gunk ing up the slider area. The white big square seal should be holding this in but seems to be failing me. Not sure what to do. But would rather not just have to bin it but at the moment I don't trust it. Any ideas?