Failed to change flight mode

Hi, I’m building my first copter:
Hexacopter with Pixhawk black cube + here 2, with a radiolink AT10 II and R12DS receiver.
This is one of my first flights and it happened the following:
Just before take off i notice that i was in stabilized mode, i changed to loiter mode, waited a few seconds and then took off, but the copter took off like a rocket in stabilized mode despite the stick of my controller being in loiter mode. I had to change back the stick to stabilized and later to loiter again to gain control and hover the copter on the air. I am reviewing the log and there is a error EKFCHECK-2, FAILSAVE_EKFINAV_1 and FLIGHT_MODE_5.
We were near a power line (30m) but we dont dont know if that could have affected the copter.
Can somebody help me to discover what happened?
You can download the log from here:
https://drive.google.com/file/d/17YXqX_myQ8NSsTqk1WqPMnm8L0Qs5uk5/view?usp=sharing
Thanks a lot.

GPS position had not been established when you attempted to switched to Loiter. See the message here when it failed and 7 seconds later “IMUx is using GPS”?

Wait longer or Arm in Loiter.