Woodburner novice - any idea what these "pellets" coming down chinney might be?

[EastMids2]

We have moved to a house with Clearview woodburner, very pleased with it. However, previous owners were "bodgers" and the board bit that covers up the chimney gap / cement seal round flue pipe is breaking away.

At first it as just a chunk of sealant that fell off and we've been shopping around for the right kind of fire cement - in the meantime (week of so)almost every day we wake up to find a couple of dozen little pea-sized cement pellets on top of woodburner. Looking back, I can remember hearing the odd pinging noise as the pellets hit top of woodburner recently when fire is lit but where are these coming from and why round? Any thoughts welcome (photo attached).

Not sure what the pellets are but I wouldn't be happy to use the stove until it was checked out. Have you seen the HETAS certificate for the original installation? Do you have a working carbon monoxide alarm?

Could they be flue lining pellets?
Like these?

I may be completely wrong but they look a bit like the beads that are sometimes used in cavity wall insulation.

YES - flue liner insulation granules (I googled images and they are identical). Thank you for solving that mystery. We will get repairs done and hopefully no more will be falling down through the gap!

If they really are bodgers then please be careful ensure you do have a working carbon monoxide alarm. One should be fitted as part of a HETAS standard installation

Thanks gassylady - no carbon monoxide alarm installed , so guess that's on the shopping list too. Just pleased to be on the way to getting everything sorted :-)