Small items can sound like major failures
The plastic or metal tip on a hoodie drawstring is called an aglet. When it slips into a gap around the drum or bulkhead it can make a repeating scrape, click, or thump as the drum turns.
Reduce the chance of it happening
Tie or secure long drawstrings before drying and check garments for loose hardware. A new rhythmic noise can also come from worn rollers, glides or an idler, so persistent noise should be diagnosed rather than ignored.
Safety note: Appliance symptoms can have more than one cause. Disconnect power before inspecting internal components. Gas-supply work must be performed by an appropriately qualified technician.