Do you have a voltmeter? Set the Vamo on the highest voltage or wattage setting and measure the center pin voltage. It should read about 6 volts. If it reads around battery voltage (3.7 - 4.2), then you may have a ground problem or possibly a bad circuit board.
This is what my Vamo reads on my TR001
mod... it reads the same with my voltmeter...
The ground to the circuit board is brought in by wire soldered to a screw in the Vamo head. Sometimes that screw gets loose, gets corroded, or simply makes a bad connection. It may sound weird, but you might try whacking the head area a little to see if it makes any difference. You may cause the ground to improve and at the very least give you a hint of what might be happening. Don't whack it too hard! And yes, I've seen this problem before.
Good luck!