I have been told that the nitrate base was plagued by yellowing and brittleness. Many of the films cannot be viewed or projected except in glass holders or one frame at a time.
The yellowing is release of NO2 and N2O4 which yellows the image and also etches silver.
Of course, they are very explosive and become more so with time. Storage in an inert atmosphere more or less fixes the problem, but who can do that outside of a museum.