Blind Spot Collision Avoidance Assist (BCA) has it's limitations. You've discovered one of them. As a workaround, you can turn your signal off when turning in multiple left-turn lanes or just ignore the warning.
Thanks. Appreciate the feedback.I think....
Blinker on = lane markers not being read
The alert noises are thinking that you are changing lanes hitting the car that's also turning next to you