It could deflinitely be leaking because of a damaged black insulator piece-
which, like other stealth parts, should be in stock for a bit after the preorders all ship out this week.
As Imeo said, it could be that your metal center pin is loosened to adjust the center pin position.
It should be snugly tightened to seal it, if you have it loosened without an o ring around the base to seal it/move the pin lower
and you have a leaky tank/etc on there, juice can seep through a bit.
If you do want the pin lower than it usually sits, put on oring and tighten the center pin snug
with a socket/wrench, don't know size offhand. Any set of small metric sockets should have one that fits.
by hand is fine

Beware the crossthreading. It's not hard
as long as you have the tools or know someone who does.
If you're fine with the center pin the way it is, the insulator could be good and the pin may just need tightening as above,
no o-ring needed. If all is in good shape, this will seal it up too.
The 2mm X1mm orings are in the ggts o ring set-
GGTS Replacement O-ring Set
Not in stock right now, but I've heard they should be soon
