[The Illustrative Man]

It's correct on this occasion though, under regen the motor is slowing the vehicle so the stresses of that are transferred through the driveshaft to the wheels. This isn't the case under braking. I'm not sure it actually supports the 'watery' or broken down grease theory though, I'm more inclined to think the parts just aren't up to it.

This is in fact the case under braking. P2 uses blended brakes - pressing the brake petal means regen, unless you're mashing it so hard it can't regen enough to slow the car.