After finding a good condition Leica M9 with a horrible condition sensor, Llewellyn extracted the CCD and put it under a microscope.

Llewellyn then used a synthetic sapphire 1 micron polish and was able to polish off most of the corrosion from the ICF. But then he found that the surface was actually pitted from oxidation, something he had never seen before.

Llewellyn carefully removed the ICF/coverglass from the CCD sensor and used a spectrometer to analyze it. This is when he got his biggest surprise.

What he found was a filter that extended down to 300nm. That filter doesn’t have coatings! Leica / Kodak used an uncoated Schott BG type glass! The coatings seal the glass. Their engineers really screwed up.

All those BG and UG types of glasses are susceptible to oxidization. Variable include time, temperature, humidity, ozone, and even the particular glass melt, but you would never put uncoated BG or UG glass in a camera and not think that one day you are going to have a problem. That Leica / Kodak would do that boggles the mind.

In 2014 response Leica actually openly lied about reason of issues (to avoid paying damages):

The sensors are equipped with a specially coated IR filter cover glass to ensure optimum imaging performance. Should this coating layer be damaged, corrosion effects that alter the filter surface may begin to appear after several years.