Thanks for the lead! Those both include this comment:

# This is NOT a complete set of PX4 parameters. These are non-default parameters
# specific to the airframe and are meant to be loaded over the defaults.

A little bit of searching turned up this reference:
https://docs.px4.io/main/en/advanced_config/parameters.html#tools

Looks like my path is to follow that guide to restore all parameters to default values, then load parameters from the files you linked to.

The drone we have shipped with a 4s battery, and ModalAI branded motors. Looks like that leaves us needing portions of each of the two parameter files. My plan is to modify RB5_Flight_V1_param_ModalAIMotors_3s_rev_A.params to include the battery configuration from RB5_Flight_V1_param_HolyBroMotors_4s_rev_A.params, and load the resulting file on top of defaults.

Recently got a RB5 UAV. We flew it indoors using position mode and voxl-vision with no issues. However when we tried to fly outdoors we had problems with vision, GPS, and the magnetometer.

All flights were using QGroundControl and a Spektrum RC controller, and running VOXL SDK 0.9

In our current state, when we boot up the drone and open QGroundControl, we only ever see "reject position mode", and see that AHRS is failing, but we don't know how to get more descriptive errors.

For context: our team has experience with ArduCopter, but this is our first exposure to PX4.

Here are the notes we took in the field while testing:

1. Flight 1: 12:48; 43 seconds. Manual flight to get used to aircraft. Lost vision accuracy which triggered a failsafe. In EKF2_AID_MASK turned off "vision position fusion", "vision yaw fusion", "vision velocity fusion".
2. Had problems going to POSITION due to failing GPS Speed Check. In EKF2_GPS_CHECK turned off Max Speed Error. Still didn't work. Calibrated gyroscope and accelerometers on aircraft. Still couldn't do position mode. Turned vision back on in EKF2_AID_MASK.
3. Flight 2: 13:22; 30sec. Lost vision went to failsafe; erratic behavior and crash.
4. More parameter stuff: Turning off vision and turning magnetometer on. EKF2_AID_MASK using only GPS. EKF2_MAG_TYPE set to automatic. ATT_W_MAG set to .1 SYS_HAS_MAG set to 1. EKF2_HGT_MODE to Baro
5. Couldn't get compass to calibrate. Tried various params. Changed CAL_MAG0_ID from 396809 to 0. Changed EKF2_MAG_CHECK to 1. Changed CAL_MAG0_PRIO to Disabled. Changed CAL_MAG0_PRIO back to High.
6. Reset to mag off and vision on. Going to test vision at low altitude. SYS_HAS_MAG to 0. EKF2_AID_MASK to 281. EKF2_HGT_MODE to Vision. ATT_W_MAG to 0. CAL_MAG0_ID back to 396809.

My instinct is that in all our fiddling we got the PX4 parameters into a bad state we don't understand, leading me to think that getting a known-good set of PX4 parameters we can load through QGroundControl would be the next thing to try, but we haven't had luck locating such a parameter file.

If there are things I can check to help with debugging, please let me know.

Thanks!