I have had vent-free logs for many years. I've just purchased a new set with the embers feature. Very pretty. What is surprising is that they puff every second or two. It's a difficult behavior to describe. By puffing, I mean that periodically they will poof, almost as if there is an air or a gas pocket that burns just a little more gas -- every second or two. Kind of annoying. Any thoughts (insufficient ember wool, packed too tightly, something else)?

I have checked for gas leaks, set is new but was a demo at the store. I don't recall it doing this at the store. Logs have been stacked according to manual, everything else works perfectly on unit.

Thanks in advance for any ideas or troubleshooting.