We’ve modified the function call to use a specific lat,lon location instead of 0,0. The documentation said that using 0,0 specifies to use the current vehicle location and there is no gps module connected to the Pixhawk.
I haven’t worked with MAV_CMD_FIXED_MAG_CAL_YAW before, so not certain. It doesn’t seem to be handled directly by ArduSub’s GCS_Mavlink.cpp, but is defined/handled by the GCS_MAVLink library. I’m not sure if there’s an explicit removal of it from ArduSub somewhere, so I’ve asked internally and will get back to you when I’ve got a response
EDIT: I was looking in the master branch instead of our release branches. It seems to be a relatively new addition to the common message set, so it’s available in ArduSub 4.1, but not ArduSub 4.0. You should be able to get access to it by downloading/installing Beta from the companion web interface’s System page