No two are alike, fishy. It could be a bad atomiser, or just one that needs to be broken in. Some of my best smokers were rubbish in the beginning. It's easy to put the tough ones aside and use the 'good' ones, but all that means is when you need your spare it's still rubbish, you have to break it in anyway, and if it does turn out to be crap it's too late to send back. Run it alongside your good one in equal measure, see if it gets better after a couple of days.
Emp