My '91 300SE starter began acting up about 3 years ago. I took it apart, cleaned and lubricated everything, and it's been fine ever since. As I remember the brushes and bearings were okay, it was just a bit of corrosion on the pull-in. These starters use a planetary gear set, and spin much faster. That's why they can be so small. But Mazda probably uses that also.

DG