I have a Win Model 100 I am working on for a friend of mine and it has a problem cocking and firing. If you charge the weapon one to two times it will fire no problem. If you charge it on the third and sometimes fourth attempt it will not fire at all but the hammer is cocked. If you wait long enough, bump it, or repeat charging it it will fire. All of the parts seem fine, and this is the only problem this rifle has. Does anyone have an idea as to what might be going on here.