@jollysea@chaos.social Any of the following (not exhaustive) can be the cause:
1. Cable not plugged in quite right, usually also will show as intermittent I/O errors in system logs. Solve by replugging.
2. Intermediate controller does not support SMART. Sometimes a problem with some external HDD cases in particular. Solve by replacing with known-good case/controller.
3. Firmware of intermediate controller is junk and sometimes randomly fails to work for SMART. Same deal, replace with known-good case/controller.
4. Weird *drive* firmware configuration. Most common in refurbished/OEM drives, especially those sold as being for a specific model of rack server. Can sometimes be fixed with hdparm magic. Sometimes requires vendor-specific (usually Windows-only) tools.