Well... It's Like This
The basic "jist" is:
Oktava Factory ships Oktava MC-319s and MC-012s to The Sound Room. The Sound Room does tests and sends the ones that failed their tests back to the Oktava Factory. The Oktava Factory then turns-around resells them to Guitar Center.
But like I said. There are plenty of threads here where I go quite a bit deeper into it.
About the cutting-out (what/where ever it is), it sounds like you might need to try and "pin-point" by eliminating possibilities. Anotherwords, for example, can you possibly try the same thing as you did before with two other mics? But from the symptoms that you explained, it could quite possibly be
the vs1880. So you might want to hold-off on giving that guy a good ole upper-cut.
Oh and most likely, if you just hook that "suspected" mic to your Mackie and simply use it "live" for 5 minutes and it doesn't cut-out on you, then most likely, it's not the mic.
Actually, I'm kinda starting to suspect a cable problem. What cables were you using and how long have you had them?
Lastly, I noticed you asked for thoughts on the MC-012s as overheads. Well, MC-012 from The Sound Room are KNOWN to be GREAT as overheads. You might look into the March issue of Electronic Musician Magazine of a "shoot-out" article of 8 small diaphragm condensers. By the way, the MC-012s in that shoot-out WERE from The Sound Room although in the article, it says they're directly from the Oktava Factory. It's a business contract issue...