After almost 16 months without, it appears that I finally have a need to wet clean my sensor...
Well, maybe... it looks like it may be a crack or scratch in the glass or some other flaw, but I can't really be sure unless I can confirm that it isn't removed by a decent cleaning. It doesn't look like the regular corner crack (it appears absolutely linear and vertical as opposed to most cracks that I've seen that are curved).
The only other possibility I can think of is the shutter may have deflected and scratched the sensor. I did have the shutter act up once that day (I could hear what sounded like only 1/2 of the normal shutter sound, and no image appears to have been taken).
Anyway... I now need to get some wet cleaning materials to see if it is merely a line of oil or something like that. I've seen some threads on the Leica Users Forum, but it was a pretty indecisive conclusion, with many different opinions expressed. That doesn't really help provide a definitive answer on what cleaning approach works the best!
So... can anyone tell me what they have used, and whether it results in essentially perfect cleaning results?