Hello John,
Thanks for sharing the results of your very interesting experiment. I can't believe anyone would want something like this except a collector for display purposes rather than anything else. The capsules I bought were very tarnished and not the sort of thing you would normally want to risk using. I have used more modern capsules after a period of about of about five years with no problems. I believe carbon dioxide is already an inert gas, so that can't have been the reason for the result.
Brian