Isaac Carlson
Minister of Fire
It could be a brick retainer, air tube, baffle support, etc... the air tubes should wiggle just a bit.
I rebuilt a stove for a guy snd added air tubes, baffle, etc to bring it up to speed. One thing I had to do was make sure everything could move and expand as it heated up. Let the stove cool, clean it out, and check all internal parts. The air tubes should be loose on at least one end so they can expand. If the brick holders are bolted in, loosen the end bolts just enough so they don't clamp it tight. The same goes for the baffle support if it is bolted.
It sounds like a bolted connection moving and I'm pretty sure you'll find it if you try.
We had a lopi years ago and it made noise when the bolted connections moved. A stove will amplify any mechanical sound.
I rebuilt a stove for a guy snd added air tubes, baffle, etc to bring it up to speed. One thing I had to do was make sure everything could move and expand as it heated up. Let the stove cool, clean it out, and check all internal parts. The air tubes should be loose on at least one end so they can expand. If the brick holders are bolted in, loosen the end bolts just enough so they don't clamp it tight. The same goes for the baffle support if it is bolted.
It sounds like a bolted connection moving and I'm pretty sure you'll find it if you try.
We had a lopi years ago and it made noise when the bolted connections moved. A stove will amplify any mechanical sound.