Hi @Nurul -
In most situations, you would not want to disable this check. However, when launching from locations with large ferrous metal objects or large engines / electrical currents present, disabling the check may be necessary if on-site location does not overcome the issue.
In such situations, I manually control the BlueBoat some distance from the launch point / interference source, and then verify the heading of the vehicle in the GCS against reality. If everything looks good, I tell the vehicle to loiter or go to a location with Guided mode. If this behaves normally, normal autonomous operation can be expected. You could apply the failsafe again at this point, but that risks the system refusing to arm at a critical moment during recovery, assuming the magnetic interference is still present !