The drive is still working fine but still makes the strange sound when spinning down. It’s only used occasionally and so it may not be the best drive to decide if it affects the performance or reliability in the long-term. The current SMART readings are as follows.
Interestingly, I did ask the very same question on the Data Hoarder Subreddit all those months ago (Link). One reply stated that they too had the same problem. In case the link doesn’t work in the future, here is a quote from Remcroft in that thread.
'It’s not a nice sound is it, mine is now a cold backup drive and I won’t buy another. It’s RZ or reds from now on.
All the AZ drives seem to do it, another one here (see link on Reddit) I RMAed mine, you can hear the one I RMAed here (see link on Reddit) the replacement was a refurb and is exactly the same so was a waste of time returning it.
The AZ drives are helium filled SMR drives, note the TRIM support. All of them seem to have this noisy spin up/down. The RZ versions of the same drives are non helium PMR and don’t have the same noise issue. I’ve got several WD60EZRZ that don’t do it.
The helium drives seem to have some sort of motor braking when they shutdown to bring the platters to a stop quicker, for some reason it’s noisy on these blue AZ drives. Maybe they get the noisy motors/bearings and the reds got the quiet ones. That’s my guess anyway but it appears to be normal as far as WD are concerned and Red helium drives don’t have the same issue.’
I did contact Western Digital support. Initially I received a standard stock-response asking to check the connections but after requesting that they listen to the audio clip, they recommended replacing the drive. I didn’t return it, mostly because of experience outlined in the Reddit reply.
I hope this helps.