You squished the o-ring, the disc looks fine. Like I said, I just rebuilt 2 setups (6 valves), I just added 2 o-rings, brought it up to temp, figured out how tight I needed it to be so it would seat the small tips in the disc and still seal the main external o-ring. Then I tightened the nut a 1/16 of a turn and backed it off, haven't had an issue since.