When you prepare the rifle before you load... Swab the bore real good. Make sure you're shooting a loose powder made for the rifle and the #11 caps. Like Black Powder, Pyrodex RS, Triple Seven, or APP. No Blackhorn and a #11 cap. You're asking for trouble.

So before you shoot, swab the bore good with isopropyl alcohol. Now swab with some dry patches. Leaving a dry patch on the loading jag, push that to the bottom of the bore. Then put a cap on the empty rifle and pop it. Make sure the secondary safety if off. Check that patch and look for a burn mark. If you have a burn mark, pop one or two more caps.. then load. You should be ready.

If you have more problems, replace the nipple for starters and I have shot tons of shots out of mine, but there is a spring that could have grown weak. Perhaps knight could help you in that department if the problem continues.