I have an old armi san marco 1858 remington new model army with a brass frame that was made in the 80's. I bought it a year ago and it was working and shooting great but a few months ago I was having problems with the hammer staying back. Now it has gotten worse and it will never stay back. I'm not sure whats wrong with it but it is annoying me beyond belief. I would really apreciate if anyone has any input or sugestions on how to fix it. Thank you.