The drive train of a Tesla is essentially a one speed gear reduction unit from the motor output shaft to the axle. No clutches, no torque converters, just a simple gear reducer with approximately a 8:1 reduction ratio. The last gear in the gear train also has the differential spider gears in it.
If they are having issues with such a simple drive train, it’s likely either the gears are undersized for the load or the bearings are and I don’t believe the drive train design is what makes a Tesla expensive.
It’s essentially a go-kart transmission without the centrifugal clutch and a gear train instead of sprockets and a chain.
Maybe Tesla underestimated the stress of accelerating a 5200 pound car from zero to 60 in just three or so seconds and how the smooth quiet and instantaneous torque of electric cars encourage drivers to do that… a lot.