Here+ RTK GPS compass/mag problem - access to other sensors


I’d like to ask for Your help in the following matter:

I’m using Pixhawk 2.1 (Edison ready) with Here+ RTK GPS module and PX4 firmware 1.8.0(stable) on a 650 Quadcopter with Nvidia Jetson TX2 as companion computer(telem2). I was flying it without issues until last week. After power on and connecting to QGC, mag0 (in HERE+, marked as external with id 73225, so I believe it’s HMC5883) started to fail with a message “Mag0 Selftest failed”. Because of that I’m not even able to arm the copter, even though I change primary compass to another one inside Cube and set parameter for mag0 as Disabled. When doing that the heading is calculated based on the internal compass but I think that due to selftest failing I’m still unable to arm the copter. Is there a way to use another magnetometer preferably in Here+(I think there are at least 3 of them, but not sure if they are on I2C) instead of the one that is failing without building the code or editing the startup file on my own?

Thank you very much in advance!