The small framed percussion revolvers are usually problematic. I know because I have had several of them (Uberti’s) most had to go back to the importer for rework or replacement. I now have an 1862 Pocket Police that needs to be sent back to Cimarron Arms for the second time because of a loose arbor, and I haven’t even fired it yet.
A very common problem I have come across with these is the barrel out of alignment with the frame. Have had 3 with this problem.
You can check for it by turning the gun upside down, trigger guard up. Holding the gun out away from you a couple or feet or more look down the length of the gun from the butt end. Two of mine had the barrel assembly angling off to the side a good 6 to 8 degrees. I would guess that Pietta has the same problem.
I’ll bet that several of you that have these small-framed open topped guns have the same defect.