After over a year of "thinking" about buying a Vixen, I finally broke down and bought one. It arrived the middle of last week.
And sorry, but no, mine has had no problem that I can see, in holding air over night. I may put an "actual" gauge on it, one that you can see...the numbers without a microscope .
If I were you, I'd just call the seller, let them know and send it back for repair. I wouldn't mess with it...I "assume" its under warranty !
Mike