This H-20 seems to use the AviaSkins version of DiffFM mod, that is not compatible with SAS version.
The only possibility to get H-20 working with our DiffFM is to add the new flightmodel He-111H-20.fmd to next SAS buttons.
However, H-16 should work without problems, so you can just comment or leave out the H-20 air.ini entry for now, or just use the older version.