Usually RT shows abnormal WB values for raws of non fully supported cameras (missing colormatrix data) or cameras with different than the expected colormatrix2 at D65 illumination in DNG exif.
This last is what happens with this DNG sample … it reports a D50 colormatrix2 … RT supposes a D65 and the calculations fail. If we change the matrix to D65 (copy from Adobe dcp or just convert the DNG with DNG converter the values calculated are temp: 5222 tint: 1.030