@rrblint, I can confirm that manual correcting the Vignette doesn’t show the circular banding. And as @sgospodarenko said in Vignetting filter causing banding - #29 by sgospodarenko, it’s definitely a bug.
This problem exits for a longer period and is still not solved 
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The difference between manual and auto correction of the Vignette is that auto uses the optical modules. And these modules should be one of the unique selling points of DXO Photolab. So I think that solving this bug should be one with high priority.