There are similar issues with Vignetting correction: Vignetting filter causing banding - DxO PhotoLab / DxO PhotoLab Windows - DxO Forums
The best way to address both problems - the color cast and the banding - is to submit a single support request via support.dxo.com and upload some sample RAW files/sidecars referencing the support ticket # (use upload.dxo.com). This will ensure that DxO’s developers will see the problem and identify the cause. They probably won’t give you a timeframe for fixing it, but if the problem is prevalent enough with Ricoh RAW files one hopes they will give it high priority.