I used a 4822 in my MIDI/CV, and wrote up some stuff about error, in case you haven’t seen it:
Here it’s shooting for a 7.25 octave range (88 notes) using amplification after the DAC.
It’s generally accepted that the threshold for distinguishing pitch differences with a trained ear is about 3 cents, so from that perspective what you’ve got is probably fine — maybe those 6 cent peaks are something to be concerned about if you’re being a perfectionist. (Note that a separate issue is beat frequencies for notes played together, and those can be audibly different for notes whose frequency difference varies across less than 3 cents. But in most circumstances I think that’s not a concern.)
Of course if you swap in a different chip you’ll get a different calibration; I tried two and one was decidedly better than the other.