Back in the old days if a razor you bought new didn't shave perfect out of the box that would be considered a manufacturers defect and most men would have returned it.
If you take a NOS piece that has sat for 50+years in it's case which is not really sealed (meaning air tight) and it's maybe in a hot humid environment I don't doubt the celluloid could deteriorate. Celluloid doesn't really need much of a reason to break-down.