I have two sets of KR808D-1 batteries. One set is from Heavens Gifts and it works beautifully--almost like a real ciggy. The other one is from a trusted vendor too but recently, I am having difficulty taking a drag unless I really take a deep breath and inhale very hard. It wasn't this bad when I first got it and I only had it for about 3 months. Is there a way to fix it?