This is caused by the defective pixel.
There are many defective pxiels in your image and doesn't be cleared by the ISP.
Check your ISP defective pixel correction function. I modify your image to point out
some defective pixels. Some defective pixels are caused by sensor itself and some are
caused by the defective pixel correction algorithm such as the white pixel surrounding
to the black pixel.
BTW. Most of the noise reduction algorithm can't cancel the defective pixel.