This is what happened: While Full Self-Driving (FSD) was engaged, the vehicle approached an intersection and appeared unable to correctly follow the roadway. Instead of following the intended road path, the vehicle continued forward, drove over the curb, and struck a road sign. The impact knocked the sign down, and the sign subsequently struck the vehicle, including the roof glass. The roof glass shattered and small pieces of glass entered the cabin, exposing both the driver and front passenger to a safety risk. Vehicle data obtained after the incident shows that the vehicle was in ACTIVE_FSD leading up to the collision. FSD changed from ACTIVE to UNAVAILABLE approximately 1.5 seconds before the crash algorithm wake-up. Significant braking occurred only very close to the collision, and no Automatic Emergency Braking intervention was recorded during the incident window. The data also shows multiple substantial steering movements shortly before the collision. Accelerator-pedal data does not establish driver acceleration as the cause of the collision. The available samples show an accelerator position of 2.0% shortly before the collision and 0.0% in the next recorded sample. The driver applied the brake shortly before impact. There were no prior warning lamps or messages indicating that FSD was about to become unavailable before the vehicle departed the roadway. The vehicle has been inspected/repaired following the collision, and vehicle data relating to the incident has bee