imu calibration and magnetic influence

Sometimes I have a 10 15 minute fight with my drone to get it in the air. For instance, sometimes it has a fit trying to get a live video feed. I will have to close the app, restart the app and if that doesn't work I'll restart the drone itself and if that doesn't work I'll reset the controller...

Finally got my P4 from crazyhobbies.com.au and ran the required updates and wanted to calibrate the IMU. I have a spirit level app in my phone so checked the kitchen bench top for level, moving the phone around to ensure no false readings. I was about to start when I remembered I had a...