I think my roaster is chewing up some beans in the front. Beans get stuck between drum and exterior. When this happens, it makes a pop sound and entire roaster vibrates. Drum alignment and spacing seems fine. With no beans, everything sounds normal. I have not roasted on it yet, just did a dry run with green beans to test the mechanics of the drum.
A clunk could be a bad front bearing I suppose but if you find beans in front of the drum that almost has to be spacing between the drum and the front plate. I know there is a procedure available for setting spacing but haven’t clue where it is. I had this issue which was specific to one bean variety and was able to adjust the spacing by trial and error by removing the thinnest spacer… there are 3 different thicknesses. Remove too many and the drum will rub the front plate.
You could see what support says and maybe they can direct you to the procedure.
I wonder if the gap between drum and door is larger when the roaster is cold. Normally there’d be no beans in a cold roaster.
I used to get beans stuck in front because I thought the door was closed but actually had another 1% further to go. I now give the door a little push before each roast.
I definitely get a light thumping after the first minute or two then as the roaster warms up a bit more it goes away, I’ve just got used to it now and there seems to be no harm. When it first happened I panicked and was looking for shiny wear or iron filings, but never saw either.