https://cameraderie.org/threads/leica-m-monochrom.37659/page-37#post-343526
My M Monochrom picked up a dark line about a year ago. I use my own code to process DNG files. One of my projects is to make it more general, let the user make an input file to specify the bad lines. It runs under Windows, batch processes all the files in a directory. I just run it on the SD card.
On my camera, and on many cameras: the lines are not dead. They lose charge passing through a "leaky" pixel. That means the line can be restored.
My M8- 12 years old now, does not have any bad lines.
From what I wrote before:
I found a recent article on restoring pixel values from columns that have been "dragged down" as happened on my camera.
The article does a good job of listing types of "bad Pixels", mine was the first type:
• Linear pixels with false bias: a category where the pixel output behaves linearly with illumination intensity or exposure time, but due to either a low or high bias compared to its neighbours, values displayed by this pixel differs considerably from the ones around it, given an homogeneous illumination;
• Nonlinear pixels: a subset of defect pixels, where the output signal displayed on an image does not relate to the illumination intensity or exposure time in a linear fashion;
• Dead pixels: are those who have very low sensitivity to illumination intensity variations, consistently presenting low grey values;
• Hot pixels: this category is highly sensible to illumination intensity variations, presenting persistent high grey values.
http://iopscience.iop.org/article/10.1088/1742-6596/772/1/012002/pdf