Personally I'd contact the Vendor but...
As of July 7 they posted on their FB page that they acknowledge the problem and are working on a fix:
https://www.facebook.com/pages/Grand-Vapor-Full-Mechanical-Mods/388426907912075
Here's someone that had the same issue- can't post the link cuz it's wordpress:
"As you may already know, some have been encountering issues with the spring action on the Grand Vapor Private v2 which has resulted in misfires, stuck buttons, and overheating. The stock spring is too weak. Even after stretching it out, the spring loses its strength after about a day or so of use.
Grand Vapor is working on sending out stronger replacement springs to solve this issue; but if you’re impatient like me and want to fix the problem now, here’s how to do it.
***DISCLAIMER***
PROCEED AT YOUR OWN RISK. I OR BAYVAPES ASSUME NO RESPONSIBILITY FOR ANY INJURY, DEATH, OR MOD FRYING THAT MAY RESULT FROM THIS TUTORIAL.
Go to your nearest hardware store and head towards the spring section. I picked up one of these.
Stock spring on left, stronger replacement spring on right
The 1/2″ outside diameter of the spring was a little too big for the button groove. I’d recommend getting a smaller diameter spring, maybe 7/16″ or even a little smaller.
A little too big for the button groove. Still works though. Get a smaller diameter.
Assemble it back onto the bottom section of the body. I had to lengthen the throw a bit in order for the pin to make contact with the battery. It will not sit flush when you push it in. Small trade-off for a consistent vape.
Lengthen the throw (screw it out a little farther).