It's factory head only, right? No RBA deck?
Is it top-fill? A mis-seated gasket up there
might allow enough "vacuum" loss, though that alone... I don't know.
Otherwise...
First guess... hers actually
is missing an o-ring. Probably some damn minuscule translucent one from inside the chimney or just below the coil. Bad news... you'll probably have to completely and carefully take yours apart as well and compare until you find the culprit.
Second guess, and the one you should do first... very carefully look at the two together, from the side, to see if there's a gap in hers between the major sections. Usually between the base/airflow section, and the deck/coil section. Even so... it
may not be visibly obvious.
There are a couple of major brand RTAs that spew on some until you use a hammer (careful!) and something like a socket to protect the 510... and tap that bitch back in place. It's probably just a mis-adjustment in the final assembly line... oops.
Really... with a mass production
factory head only tank... there aren't a lot of possibilities.
(Something I installed the wick in, on the other hand.
)