caliberatate results in an "Nan" error

[jaxkingdom]

I caliberatate my mpu9250, it's result as follows, but when run kalman by .json file, the yawl info return Nan,why?
%Run complete_caliberation.py
Accel calibration starting
Acceleration calibration is starting and keep placing the IMU in 6 different directions based on the instructions below
Put the IMU in 1 position. Press enter to continue..
[-0.28412242 1.1355439 10.50506506]
[]
[]
[10.505065058365755]
Put the IMU in 2 position. Press enter to continue..
[ 1.13468195 -1.13422702 -8.98501074]
[]
[]
[10.505065058365755, -8.985010735637445]
Put the IMU in 3 position. Press enter to continue..
[ 0.5851727 -9.76096913 1.58245638]
[]
[-9.760969127946899]
[10.505065058365755, -8.985010735637445]
Put the IMU in 4 position. Press enter to continue..
[-0.30771249 9.53003063 -0.44961807]
[]
[-9.760969127946899, 9.53003062668803]
[10.505065058365755, -8.985010735637445]
Put the IMU in 5 position. Press enter to continue..
[-9.43546681 -0.34059852 0.18578156]
[-9.435466814373997]
[-9.760969127946899, 9.53003062668803]
[10.505065058365755, -8.985010735637445]
Put the IMU in 6 position. Press enter to continue..
[9.90379053 0.32024079 1.38590037]
[-9.435466814373997, 9.903790533302814]
[-9.760969127946899, 9.53003062668803]
[10.505065058365755, -8.985010735637445]
Accel calibration Finisehd
[ 0.23748847 -0.11740262 0.76485966]
[1.01420647 1.01674357 1.00635832]
Mag calibration starting
/usr/local/lib/python3.7/dist-packages/imusensor-1.0.1-py3.7.egg/imusensor/MPU9250/MPU9250.py:400: RuntimeWarning: invalid value encountered in double_scalars
Mag calibration Finished
[-4.11800666 25.14775067 5.39850273]
[[nan nan nan]
[nan nan nan]
[nan nan nan]]
[1. 1. 1.]