As the old board is not reliable a new board with new sensors has been designed. As MLX90609 is out of production ADXRS450 is the new choice. It is pretty expensive but has continues self test and potential failure can be detected. Besides the self test the gyro is factory precalibrated, accurate and comes also in LCC package.
Finally, I have implemented TaitBryan angle conversion and added simple EFIS display to the service application. Will be handy for semi automatic flights. Some minor things are not implemented yet but, generally, every essential information is displayed.
Added a short video showing magnetometer calibration algorithm working real-time. See Calibration section.