Older traditional papers will loose contrast. Older MG papera will loose upper end contrast. I used Ilfrod MG FB many years old with success
MGIII RC paper has always been bad when I have tried it.
When trying them out for fog, pick from the middle. Contact with the cardboard or plastic can change the behavior of the top sheet.
Well, he said it was all out of the packages and in the paper safes. When he sold the safes, he put the paper back into the packages. My guess is they are well shuffled. Probably try several sheets randomly.