Steering angle sensor -15 degres after zero point calibration

My 2008 Sienna has TRAC OFF and VSC light on every 2-3 months. These lights will disappear after restarting the car. Techstream shows the code C1290: abnormal zero point of steering angle sensor. The zero-point calibration was performed successfully using Techstream (Reset memory then test). However after the calibration, the Data List shows Steering Angle Sensor -15 degrees and Zero Point of Steering Angle 0 degrees. See attached picture, please. Does someone know what is going on? Thank you.