I've fixed this problem a few times (on different drives) by giving the drive a not so gentle thwack with a hammer. The trick is to hit it on the long side, which tends to dislodge the stuck heads/arm. If you hit it on the top or bottom, you're likely to break something, and hits on the short side aren't likely to achieve anything at all.
Many jobs ago we had an outage caused by 2 drive failures in a Raid 5 system, that was resolved by banging the drives on the ground a couple of times before putting them back in.
If I still worked with physical servers I'd be carrying around a rubber mallet to apply "percussive maintenance"
I've used this method after the fridge/freezer method failed. It seems less likely to cause data loss than using a magnet to move the head as in the article.
