HDD doesn't spin down properly on shutdown

When shutting down the PC, an internal HDD has the power abruptly cut before it can spin down. This is audible - it sounds exactly like an external HDD being unplugged while it’s running.

This started happening a few weeks ago, but I haven’t made any changes to the system. What might be causing this?

Failing motor in the HDD.

SMART status isn’t reporting anything wrong, but it’s a possibility. Is there a log file somewhere that might have more info?