A similar file imported into C1 has dimension 7360x4912 and when saved as dng is 72Mb.
the above NEF file saved as tiff is 202Mb so it would appear that C1 is opening the NEF file and not the jpg
the dng and tiff files saved from C1 will now open in Photoshop without the 'could not complete...unexpected end of file was encountered' message
The original NEF file opened with Graphic Converter as full size file