You're doing something I would never do gregrn. I'll hunt with a load in a clean barrel for days, weeks, or months without worry. But once I fire that gun and reload, that second load has to come out at the end of the day. I would never hunt a few days longer witha second load in a fouled bore. I think the fouling in your bore and nipple is gathering enough moisture to prevent the first cap from igniting the charge when you try it a day or two or three later.