Metal Shavings

I’ve been roasting on my Bullet for about a year now and just experienced a roast where I heard rubbing start in the back and noticed in the drum, in the chaff collector and all over the back by the exhaust that there were metal shavings.

What could this possibly be?

One thought, if you haven’t checked…did you leave the chaff filter basket protruding too far, so that the fan slightly rubbed it?

How big are the shavings?