They replaced everyone's bolts, but only did the mounts if they were broken. Those new bolts were stronger...the original ones, under certain circumstances could shear off. At the same time, they reprogrammed the logic to adjust the reaction when they detected the wheel(s) off the ground, and how much they might accelerate. The abrupt stop or slowdown when the tire reached the ground is what could damage the mount or bolt - the electric motor can accelerate quite quickly! In some ways, it was probably better for the bolt to shear rather than the mount, but avoiding both was the goal. If you've ever driven in Germany, you'd probably agree their typical roads are well maintained. This didn't show up in the years of testing prior to release. Parts of the US have some pretty sorry roads, and IMHO, the average driver is less attentive, so curbs, potholes, etc., did it in. I had a similar engineering issue with an older Audi...our fuel is allowed to have more sulfur than Europe, at least in Germany. It caused the fuel sensors to fail. It took them two redesigns to get a set that actually worked with our fuel...only started to show up after 2-3 years.