After doing the CLA on my own EM, I'd have to disagree with this. They are simple mechanisms with very few gears, and levers. Unless there's damage caused by abuse, there shouldn't be any "parts" problems, that a good cleaning and lubrication shouldn't fix. The only thing I found "overly " cheap were the springs that held the focus screen in place. They both broke on me, requiring some fabrication of new ones. The brittle leatherette covering came off in pieces, I plan on replacing it, if I keep the camera.
What generally happens is someone tinkers with them, not having the proper tools. There are a lot really tiny soft brass screws, that require JIS drive screwdrivers, if you don't use the right tool you will strip out the slot. Unless you have the eyesight of an eagle, you need a magnifying headset with lights.
The hardest part for me was adjusting focus on the lenses. Managed to cobble a diy collimator, that has it close.