External Drive Orientation

I've noticed an odd quirk with some of my external SATA HDDs. They work fine when horizontal, but not so much at an angle. They're all WDs of various capacities, acquired over the last 8 years. One of them is perfectly fine either flat or on end (90 deg), but the others don't like it so much. Has anybody else come across this or have any insight into what's going on? I was under the impression that the spindles didn't react like a gimble, but these drives are almost proving this theory wrong.

read this



gravity can cause the read head to move slightly if used in one position for a long time and when you change orientation it does not line up exactly any more.  This would be related to older tech more than current tech

I wondered about that as it could relate to resonance created by the natural operation of the drive.