This might be old lore, but I remember many years ago that someone told me that when a spinning disk has been up to temperature for a long time there's a bit of

This might be old lore, but I remember many years ago that someone told me that when a spinning disk has been up to temperature for a long time there's a bit of lubricant that is vaporized and evenly distributed everywhere (like the halides in your halogen headlamps). But when it stops spinning that stuff cools down and gets sticky and ends up sticking the heads to the disk so that it can't get going anymore. Don't know the truth to that, but it seemed like a reasonable explanation at the time.