I have purchased * Homedic Total Comfort Ultrasonic Humidifiers from Costco and I've ha...

I have purchased * Homedic Total Comfort Ultrasonic Humidifiers from Costco and I've had the same problem with all * of them. I don't know if it was a bad batch that Costco got but that's really kind of weird that I've had the same problem with three different humidifiers. It's a two gallon dual tank so one gallon on the right side and another gallon on the left. The left gallon goes down fine on all of them but the right doesn't work. It just stays full so after the one gallon on the left is out, it shuts itself off. It just doesn't release the water from that right tank. One of them worked for the first week the way it was supposed to. The second one worked for a couple of days the way it was supposed to and the third one was bad right out of the box. Can you please tell me if I'm doing something wrong or if I've just picked up three defective machines?