The angle data read by the MPU9250 using the MPL library is unstable.

The angle data read by MPU9250 using IIC communication and MPL library is unstable. The three angles of pitch, roll, and yaw vary greatly, sometimes changing 3 to 5 degrees in ten minutes.
The magnetometer has been calibrated when viewing the angle data, that is, accruary = 3. The chip is placed horizontally when using it. I don’t know where the program is wrong. Please help to solve it. Thank you very much. The program is attached.The hardware uses stm32F4 and the platform is MDK5.