Brother Dean Romig's advice about having a good double gun man who knows Parkers look it over is "Spot On"-- Wear at the hinge pin where it makes contact with the milled "C-hooked" radius in the lug is common with doubles that have seen some usage, and can be corrected-Many older quality double guns were fitted at the breech by patient craftsmen with smoke lamps, files and stones- all hand work.
Parkers and LC Smiths were the double guns I grew up with in the family- but I recall my Grandpa's best friend and hunting partner shot a AH Fox- 12 engraved ejector gun with Krupp barrels- My Grandpa usually shot Winchester paper ranger bird loads, one day he bought a box of UMC instead-
Turned out that the rim dia. of the UMC hulls was about 0.0015" larger than on the Winchester shells- my grandfather owned a machine shop and "miked" the shells that night- as only the Winchester shells would allow Mr. Bontrager's Fox to close properly- that's an old time example of how precisely our older doubles were fitted-
If your Parker has selective ejectors, you'll notice a set screw in the end of the doll's head barrel extension- it might be possible that the milled slots in the extension are in need of attention. I have never (yet anyway) heard of a barrel rib extension on a Parker, AH Fox or LC Smith being part of any possible "off face" but as the wise men say- "Never Say Never"-
If you care to give a location, I am sure some of the members here can recommend a good competent gunsmith in your area to check over your "Old Reliable"--