Guys I'm having exactly the same problem with my RSST. Note that the DID does not have the problem.
The culprit in my opinion is the narrow wick hole: when you suck the vacuum does pull up the juice. This is easely dimostrated: just clean up your top deck, then put the cap on and give 4/5 strong draws WITHOUT activating the atomizer. Reopen the cap and the juice is there.
A solution would be to remove the insulator to make the wick hole bigger (like the DID), or make an even thinner wick.
But if you think about it for a moment, this is not necessarily a problem, it maybe a feature. I usually vape with my cap hole facing down, so I thought if I suck up the juice I will never get a dry hit. So I just use my mod casually without bothering where the hole is. This helped a lot vaporising the juice in excess and I don't have to check my air hole everytime : )
