Adaptive Cruise Control problems of the 2017 Toyota Highlander

The radar cruise control system on my 2017 Toyota Highlander is not functioning properly and creates a safety hazard. When initially setting the radar cruise control, the system works as expected. I can accelerate to a desired speed, press the “set” control, and the vehicle maintains that speed correctly. The problem occurs when I try to increase the set speed. After setting an initial speed (for example, 45 mph), I accelerate to a higher speed (such as 65 mph) and press the “set” control again to update the cruise setting. Instead of setting the new speed, the system reverts to the previously stored speed. When this happens, the vehicle rapidly decelerates and applies braking to return to the lower speed. This sudden and unexpected braking creates a dangerous situation, especially on highways, as it can put surrounding drivers at risk of a rear-end collision. I have tested this multiple times and experience the same result each time. This issue only occurs when using radar cruise control and does not occur with standard cruise control. Note this has been an ongoing issue since the day I purchased my vehicle in January 2017. I notified the dealership about the issue and they stated they would open a case with Toyota.