Went shopping and left my vtube covered in my car. Came back to my car got on the road and started to vape and my setting was 3.0v instead of my normal 4.8v. I moved it back up to my regular voltage of 4.8v took a puff and again it went back down to 3.0v? Did this three of four times and after about ten minutes it is staying at my regular voltage of 4.8v? Any reason why it would do this out of the blue?