Thanks. This is only when I tighten the nut. It sits flush by hand.

I am missing something obvious here but I haven't been able to figure out what it is. The peanut fitting on the AC accumulator isn't sitting flush if I tighten the retaining nut. Is there a shim that I am missing or a different oring I should use? This is on a 2000 F-250 7.3. This started as a compr...