Hello, Ami.
So you took your vehicle to the dealership, they analyzed it and could not discover the problem. Yet they want you to take it back?
What are they intending to do differently?
You may want to call the Lexus customer service number:
Phone: You can call Lexus Customer Service at 1 (800) 255-39871. They are available Monday to Friday from 5 a.m. to 5 p.m. PT.