On [XXX], while using Full Self-Driving (FSD) to drive to a hospital in Oak Park, Illinois, the vehicle experienced sudden unintended acceleration during the disengagement of FSD. As the vehicle approached the hospital area, I initiated disengagement of FSD to manually enter the parking area. Duringâor immediately afterâthe disengagement, the vehicle suddenly accelerated at full power without warning, causing an immediate loss of control and a collision with a nearby fixed structure. No system warnings or alerts were issued prior to the event, and the acceleration was so abrupt that manual intervention was not possible. This occurred in a low-speed, street-level environment where no acceleration was intended or expected and does not correspond to any normal driver input. Based on review of preliminary incident data provided by Tesla, there appear to be irregularities during the FSD-to-manual control transition, including missing or invalid input values, gaps in accelerator/brake/steering signals, and speed readings inconsistent with the crash severity. These indicators suggest potential instability in the real-time control system during disengagement. This report is submitted due to concern that sudden unintended acceleration during FSD disengagement may represent a safety defect with potential risk to drivers and the public. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)