Just rebuilt a Peppina (a 1976 based on the date stamp on the bottom). Fired it up to pull a shot, and after removing the PF, the group dripped steadily. I put a container under it and observed for a few minutes, until it became apparent that the drip wasn't going to stop until the boiler was emptied.
I'm a fan of the search function and have read through several Peppina threads, including the 'Peppina Redux' mega-thread. Nothing about this issue. I suspect this is the small flat washer, not properly seating and sealing, and allowing water to continue through the group. Before I take it all back apart, any thoughts on which way it might need to be adjusted? OE and others note tightening the screw that holds the washer in place just until it it is tight and the washer is still flat, not cupped. So I am not sure if I have overtightened or undertightened. I could see either one being problematic. Over, and the washer is cupped and cannot seal completely due to the outer edges always being pulled away by the center. Too little, and it never would sit flush to seal.
But it isn't a very complicated thing, and when I rebuilt a Comocafe (same system), the fine tuning was with the group gasket, not the flapper washers. Could something else be causing the drip? Or perhaps the washer isn't pliant enough?
I hope this isn't potentially the larger flapper washer, since that would mean removing the kettle again. I guess that could also be mis-adjusted as above, allowing water through the cylinder past the piston and into the group.