Published in my Guide to Leica is an example of a bad pixel column on the M9P sensor. All digital sensors are susceptible to such issues, but since most DSLRs contain an anti-aliasing filter which blurs away the issue, it rarely becomes visible. But the Leica M9 / M9P does not have an anti-aliasing filter, so any such defects show up.
Sensor defects can generally be mapped out in software, so my Leica M9P is at Leica being fixed. I will of course verify that the map-out does not result in some other oddity.