I have a wierd issue with Cube Orange and Here3 GPS compass.
Here3 is attached to CAN1 on Cube Orange. Mission Planner shows its compass dev twice and also in HW ID database it appears as PRIO1 and PRIO3. Cant really make any sense of it. Setting BRD_BOOT_DELAY to 5000ms did not help. Arduplane is 4.1.0-dev.
I have not seen this before. But you may try to reset all parameters to default and reflash the firmware on Here3.
Also verify if this happens on stable ArduPlane as well.
Traced down the root cause: COMPASS_PRIO3_ID contained same ID as COMPASS_PRIO1_ID. Probably slipped in at some point - when messing around with compass discovery/ordering. Setting COMPASS_PRIO3_ID back to 0 cleared the issue.