I am writing to report a significant safety concern involving the second-row seat in the 2021 Toyota Sienna. The issue involves the seat base not locking securely into the floor. As a result, the seat remains unstable and sits at approximately a 45-degree angle, rendering it unsafe and unusable. This malfunction poses a serious risk to passengers, especially during braking or a collision, as the seat is not properly anchored. It also prevents the safe installation of a child car seat or booster. Despite this being a clear safety issue, there has been no recall issued by Toyota, and customer reports online suggest this is not an isolated incident. The inability of a seat to lock into its designated position is a fundamental failure in vehicle safety design. The vehicle has not been inspected and no warning of the issue was given.