William Sommerwerck wrote:
Yesterday I went to clean some Command LPs from Scott Dorsey, and fix the
broken spindle on the record-cleaning machine (a Nitty-Gritty Mini-Pro 2).

To my surprise, the motor was jammed. (I rarely listen to LPs, and haven't
used the machine in some time.) Turning it with the power on freed it.

I was just wondering... Other than the obvious (gunky grease), is there
anything else that would cause a motor to jam?

worn bearings can cause the rotor on some motors to jam into place. I've
had to add spacers to induction motors to get them to run again when the
axial play becomes too great, and non-bearing surfaces start to rub.