TauDEM: Missing cell area contribution

I have a terrain, that looks like the below:

The geotiff file can be found here

I run the geotiff file with the taudem, with the threshold value =10

1. PitRemove.exe Site6.tif
2. D8FlowDir.exe -p Site6.tif -sd8 Site6sd8.tif -fel Site6fel.tif
3. aread8.exe -p Site6p.tif -ad8 Site6ad8.tif
4. Gridnet.exe -p Site6p.tif -plen Site6plen.tif -tlen Site6tlen.tif -gord Site6gord.tif
5. PeukerDouglas.exe -fel Site6fel.tif -ss Site6ss.tif
6. aread8.exe -p Site6p.tif -wg Site6ss.tif -ad8 Site6ssa.tif
7.  Threshold.exe -ssa Site6ssa.tif -src Site6src.tif -thresh 10
8.  Streamnet.exe -fel Site6fel.tif  -p Site6p.tif  -ad8 Site6ad8.tif -src Site6src.tif -ord Site6ord.tif -tree Site6tree.dat -coord Site6coord.dat -net Site6net.shp -w Site6w.tif

I would expect that all of the original cells in the original terrain should be contributing to the flow path, because there is no edge contamination, ie: no drainage is inwards from the boundaries or areas with no data values for elevation. For this terrain, the elevation levels peak at the center and then going downwards radiating from the center.

But when I examine the final output, ie: site6w.tif, it seems that there are quite a lot of missing cells ( the contributing cells are marked in dark, and since they are nowhere representing all of the possible contributing cells, we can thus infer that there are lots of cells that are missing), as shown below:

TauDEM seems unable to decide for a lot of cells, where the flow contribution is going to.

I also find that with or without the -nc parameter, the outcome is almost the same, there are still a lot of missing contributing cells.

I’ve no idea why lots of contributing cells are missing, any suggestion?