Gets binding error calibrating Compass

I know… old firmware.

Its an old DJI F550 with an APM 2.5 with external uBlox 6 GPS/Compass.
Internal Compass is disabled (cut on the board).

It all works fine with the latest firmware 3.2.1 that works for the board, without the barometer that is insane, it gives juming Alt Holds for example.

People say that 3.1.5 is more stable with the barometer, so I loaded it and now it is impossible to calibrate the compass. I get the attached error message.

Well… I cant find the attachment-function… ?!

Anyway, the error says:
An unexpected error has occured when binding of a dynamic “arrangement” (translated from the swedish error).
vid Microsoft.CSharp.RuntimeBinder.RuntimeBinder.Blind(DynamicMetaObjectObjectBinder payload, … a lot of text.

/MickeM

Dont bother. The solution is: Skip 3.1.5, use 3.2.1 or any hardware that is newer than this setup.