We were given an ultrasonic mist diffuser for Christmas and have used it a handful of times. It was fine the first couple of times, but now it smells of wet dog plus the essential oil when it's on, which is very unpleasant. I've emptied it and taken it apart to dry everything out, but surely this can't be right? I must have another read of the instructions to check whether you should empty it if you aren't going to use it for x amount of time.