Mac Mini M4 USB-C audio random thumping noise and a past history of randomly dropping the TimeMachine HDD

Problem: The Mac Mini creates random sharp audio thumps in the attached audio-system speakers. The mini also has had a history of disconnecting the TimeMachine HDD, also randomly. There is no apparent underlying pattern to the thumps nor was there for the HDD disconnects which seem to have decreased on frequency: Thumps may occur in a cluster in an hour for one day, be spread throughout the day or go for days or weeks without happening. Cables are not the obvious problem; wiggling connections and changing ports makes no difference. Same was true of the TimeMachine drops/disconnects.

System: 2024 Mac Mini M4 16GB/1TB with macOS 15.6. Peripherals include a Dell S2715H monitor attached via HDMI, a USB-C 2TB HDD for TimeMachine (rear port) and a USB-A audio system connected to a front port through an Apple USB-A/USB-C cable.