How old is it?
Gunpowder deteriorates, a rule of thumb for shelf life is 45 years for single based and 20 years for double based.
The rate of deterioration is directly related to heat. Heat breaks down gunpowder.
If the cases have water migration inside; dump the stuff. NOx outgasses from gun powder, some of it will convert to nitric acid gas in the presence of water. That will corrode the case internally.
If I'm not shooting, I'm reloading.