Here+ compass not calibrated

My RMRC Anaconda has 16 flights and over 4 hours of air time without any problems. No hardware change and in the same airfield as other tests the plane will not arm because the compass is not calibrated. I have tried calibrating with qgroundcontrol and mission planner (both latest versions), I even tried both onboard calibration and live calibration with a reboot after each. QGroundControl shows green for internal and external compasses after calibration. The cable between the Here+ and the Cube looks fine and a connection test seems there’s no breaks in the wires.

Disabling the external Here+ compass and running on internal allows arming (after another compass calibration) but I’d rather use the Here+ if I can.

I have other Here+s but they are mounted and glued to other working aircraft so I’d rather not swap them out if I can help it.

Anyone know of anything else I can check?