Blue cast or sheen in Gloss Chroma Optimizer

Piezo Pro inks in a 9800.
Getting a faint bluish sheen in the Gloss Optimizer when printing to baryta.
Almost looks like a the kind of sheen from oil that is floating on top of water.
I am assuming this is some kind of ink contamination in the GO channel and I need to flush out that channel?
But before I go ahead and waste a bunch of GO I was wondering if it could be anything else?

Note - the 9800 only has a single K channel and to switch from MK to PK requires flushing that channel. The majority of the time i print MK, so generally its not a problem, but a client has a large PK project so have done the switch. But most of the time the GO channel is not used (in MK mode). So is it a fair guess that some ink has traveled back from the head into the dampers and that is where the contamination is coming from? Or could it be something else?

Thanks!
Neil

This could be some contamination . . .

you may do better on this particular printer and paper combo to use straight GO instead of GCO. In 2018 I re-engineered PiezoPro to be able to print with both GCO and GO chemistry . . . GO has more acrylite in it . . .

-Walker

thanks Walker
I will hopefully soon be upgrading the 9800 to something more current.
In the short term, seeing that I have a client project pending, will the GCO work, in theory, on the 9800 and the Hahnemuhle PhotoRag Baryta? Is there something in the chemistry that is not compatible?

Should be fine as it’s been since 2016 . . . I see a tiny sheen at some angles in natural window light . . . not see-able in gallery light . . .

-Walker

ok thanks I will try purge the GCO channel and see if that helps