No worries, it's just a BB activated switch. Shake it to the left then shake it to the right. If you shake it with all of your might then it goes into full auto mode.
...Assuming that it passes all of the other timing and action tests(member dfariswheel has posted a long list of how to do a full check-out on a V spring action) I wouldn't worry about it.
Dfariswheel is very knowledgable, and generous with his advice. It might be possible for you to contact him through this forum or the Colt forum for further advice. I would post your question on the Colt Forum also.
I am no expert, but I don't think the Python should rattle. I am away from my guns now and can't check my own.
Problem solved! I got brave, dissasembled the gun, cleaned it, lubricated it and from rattle snake I have a Python again!
Saddly I nicked one screw just a bit
I was also shooting today - 12 shots on 11 yards (10 meters)
Gun is definetly a solid shooter!
Im just bit surprised, that it locks exactly in the moment when hammer starts to fall, just in the last "second" before the shot. Bit unusual for a Smith or Ruger shooter.
I was bit shocked by craftsmanship inside the Python. Even poorly made CZ-75 from 1990s dont have such tooling marks. But they are only on non functional surfaces, but anyway I ecpected something better from the "finest revolver" ...