Failed Spindle Motor Bearings
Bearing issues can cause problem that range from induced noise into the subsystems all the way to being completely frozen.
The latter is a very complex procedure requiring the media stack to be transplanted into a "donor" drive.
Bearing issues are caused by normal wear, overheated host computers and impact
seen commonly in tipped over external drives.
The transplant procedure is performed in a clean room environment only by highly skilled engineers.