Schneideritis or not ?

[Andrea Gazzoni]

I bought this Schneider G-Componon 240mm lens three years ago, it was in perfect condition when it arrived. The lens is stored in an apartment, in a cardboard box, everything was fine until April 2023 when I observed strong degradation of the internal paint. I figured it was Schneideritis. Now seven months later I looked at the lens again and found it in a surprisingly better state. However, some traces of paint peeling are visible but much less serious than before.
Any idea what could have happened?

[xkaes]

The current shot looks like the traditional stuff. I have no idea what that April shot is.

[Michael_qrt]

I've noticed on a couple of my lenses the Schneideritis seems to vary with the ambient atmospheric conditions. I think it has to do with the humidity and temperature but I haven't made systematic observations to pin down exactly what causes the effect. Anyway I've never seen any noticeable image degradation when shooting even when the schneideritis is at its most severe.

[Drew Wiley]

Most likely expansion/contraction stresses due to serious temperature and humidity swings. Those symptoms should tell you to be more cautious storing your lenses, since mold might follow. But as it is, Schneideritis per se has little or no effect on printed images themselves.