I bought Vicks V4500 a couple of months ago. Overall I like it. Few times in the past, mist was NOT present. (tank was full of water) I set up at the second level and the setting of humidify was about 95%. The motor was still running but there were not mist and the water tank was almost up to the top after running overnight. I wiggled the water tank a bit and water started to gobble down to about half the tank. What can I do?