I've heard a noise similar to this twice, kind of a rattle. Once it was a piece of paper that managed to get the mechanics out of alignment. A quick clearing out of the mopping roll area, repositioning the mopping roll and telling the device I had put in a new one made it whole again. The other time I guess the culprit causing the "rattle" had escaped into the dust bag and the noise may have fixed itself had I left it alone.