This is a very common comment across all forums but you may want to ask your LBS for some exact numbers? If you sell 10 Yamaha powered bikes and 200 Bosch powered bikes, Yamaha returns will look excellent!According my local e-bike dealer who sells e-bikes equipped with Bosch and Yamaha motors Yamaha motors are the most reliable ebike motors. All clients motor related returns and complaints are about Bosch motors and they have zero Yamaha motor related issues.
If we go by these figures TranzX, Continental, FAZUA etc. would be the best motors in the world.
Don't get me wrong, I have to agree, the Yamaha is a very good motor, but there is only a small % out there comparatively speaking.