The mark around the cylinder comes from one of two things.
Either the bolt is not disengaging properly or the person who is handling the pistol is manipulating the action in a way the permits the cylinder to turn even though the bolt is not retracted.
As you cock the pistol examine the bolt closely. When the pistol is at half cock, the bolt should retract in such a way that it does not contact the cylinder at all. If it does some work on the bolt will correct the problem. The way you are describing yours, it is operating correctly.
Then, when the hammer comes all the way to full cock, the bolt snaps into place holding the cylinder in battery. But it is possible to get the bolt to snap into its extended position even though the cylinder is not in battery. So then with the bolt extended, the cylinder moves and the bolt scores the cylinder.
My reading of history convinces me that most bad government results from too much government. Thomas Jefferson