I just bought a vintage 1911 hammer for my build and I installed it simple as can be. However when checking for safe function of the hammer I noticed that I can fully pull the trigger and "fire" the pistol with the thumb safety engaged. I haven't encountered this problem before and I couldn't find anything helpful on the internet so I'm not quite sure what the solution is. The hammer I had on the gun previously had no issues at all so I'm not sure if the safety needs to be fitted with the hammer or if the hammer is just junk. Any thoughts?